Create a Svelte 5 counter component with increment and decrement functionality.
Use Svelte 5's `$state` rune for reactivity. The component should have increment/decrement buttons and display the current count starting at 0.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import userEvent from "@testing-library/user-event";
import Counter from "./Component.svelte"; // Your component that is written using the ResultWrite tool
describe("Counter component", () => {
test("renders with initial count of 0", () => {
render(Counter);
// Use data-testid to get elements
const countElement = screen.getByTestId("count-value");
const decrementButton = screen.getByTestId("decrement-button");
const incrementButton = screen.getByTestId("increment-button");
// Check initial state
expect(countElement).toHaveTextContent("0");
expect(decrementButton).toBeInTheDocument();
expect(incrementButton).toBeInTheDocument();
});
test("increments the count when + button is clicked", async () => {
const user = userEvent.setup();
render(Counter);
const incrementButton = screen.getByTestId("increment-button");
const countElement = screen.getByTestId("count-value");
// Initial count should be 0
expect(countElement).toHaveTextContent("0");
// Click the increment button
await user.click(incrementButton);
// Count should now be 1
expect(countElement).toHaveTextContent("1");
});
test("decrements the count when - button is clicked", async () => {
const user = userEvent.setup();
render(Counter);
const decrementButton = screen.getByTestId("decrement-button");
const countElement = screen.getByTestId("count-value");
// Initial count should be 0
expect(countElement).toHaveTextContent("0");
// Click the decrement button
await user.click(decrementButton);
// Count should now be -1
expect(countElement).toHaveTextContent("-1");
});
test("handles multiple clicks correctly", async () => {
const user = userEvent.setup();
render(Counter);
const decrementButton = screen.getByTestId("decrement-button");
const incrementButton = screen.getByTestId("increment-button");
const countElement = screen.getByTestId("count-value");
// Increment twice
await user.click(incrementButton);
await user.click(incrementButton);
expect(countElement).toHaveTextContent("2");
// Decrement once
await user.click(decrementButton);
expect(countElement).toHaveTextContent("1");
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"code": "<script>\n let count = $state(0);\n\n function increment() {\n count++;\n }\n\n function decrement() {\n count--;\n }\n</script>\n\n<div>\n <button data-testid=\"decrement-button\" on:click={decrement}>-</button>\n <span data-testid=\"count-value\">{count}</span>\n <button data-testid=\"increment-button\" on:click={increment}>+</button>\n</div>",
"desired_svelte_version": "5",
"filename": "Counter.svelte"
}
{
"content": [
{
"type": "text",
"text": "{\"issues\":[\"Using `on:click` to listen to the click event is deprecated. Use the event attribute `onclick` instead\\nhttps://svelte.dev/e/event_directive_deprecated at line 14, column 41\",\"Using `on:click` to listen to the click event is deprecated. Use the event attribute `onclick` instead\\nhttps://svelte.dev/e/event_directive_deprecated at line 16, column 41\"],\"suggestions\":[],\"require_another_tool_call_after_fixing\":true}"
}
],
"isError": false,
"structuredContent": {
"issues": [
"Using `on:click` to listen to the click event is deprecated. Use the event attribute `onclick` instead\nhttps://svelte.dev/e/event_directive_deprecated at line 14, column 41",
"Using `on:click` to listen to the click event is deprecated. Use the event attribute `onclick` instead\nhttps://svelte.dev/e/event_directive_deprecated at line 16, column 41"
],
"suggestions": [],
"require_another_tool_call_after_fixing": true
}
}
{
"code": "<script>\n let count = $state(0);\n\n function increment() {\n count++;\n }\n\n function decrement() {\n count--;\n }\n</script>\n\n<div>\n <button data-testid=\"decrement-button\" onclick={decrement}>-</button>\n <span data-testid=\"count-value\">{count}</span>\n <button data-testid=\"increment-button\" onclick={increment}>+</button>\n</div>",
"desired_svelte_version": "5",
"filename": "Counter.svelte"
}
{
"content": [
{
"type": "text",
"text": "{\"issues\":[],\"suggestions\":[],\"require_another_tool_call_after_fixing\":false}"
}
],
"isError": false,
"structuredContent": {
"issues": [],
"suggestions": [],
"require_another_tool_call_after_fixing": false
}
}
{
"content": "<script>\n let count = $state(0);\n\n function increment() {\n count++;\n }\n\n function decrement() {\n count--;\n }\n</script>\n\n<div>\n <button data-testid=\"decrement-button\" onclick={decrement}>-</button>\n <span data-testid=\"count-value\">{count}</span>\n <button data-testid=\"increment-button\" onclick={increment}>+</button>\n</div>"
}
{
"success": true,
"message": "All 4 tests passed!",
"passed": 4,
"failed": 0,
"total": 4,
"duration": 1232,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
}
}
{
"content": "<script>\n let count = $state(0);\n\n function increment() {\n count++;\n }\n\n function decrement() {\n count--;\n }\n</script>\n\n<div>\n <button data-testid=\"decrement-button\" onclick={decrement}>-</button>\n <span data-testid=\"count-value\">{count}</span>\n <button data-testid=\"increment-button\" onclick={increment}>+</button>\n</div>"
}
{
"success": true
}
<script>
let count = $state(0);
function increment() {
count++;Create a Svelte 5 number doubler component that uses the `$derived` rune.
The component should have a number input starting at 5, use `$derived` to calculate the doubled value, and include a button to increment the number.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import userEvent from "@testing-library/user-event";
import NumberDoubler from "./Component.svelte";
describe("NumberDoubler component", () => {
test("renders with initial state", () => {
render(NumberDoubler);
expect(screen.getByTestId("number-value")).toHaveTextContent("Number: 5");
expect(screen.getByTestId("doubled-value")).toHaveTextContent("Doubled: 10");
});
test("updates doubled value when number increments", async () => {
const user = userEvent.setup();
render(NumberDoubler);
await user.click(screen.getByTestId("increment-button"));
expect(screen.getByTestId("number-value")).toHaveTextContent("Number: 6");
expect(screen.getByTestId("doubled-value")).toHaveTextContent("Doubled: 12");
// Click again
await user.click(screen.getByTestId("increment-button"));
expect(screen.getByTestId("number-value")).toHaveTextContent("Number: 7");
expect(screen.getByTestId("doubled-value")).toHaveTextContent("Doubled: 14");
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"content": "<script>\n let count = $state(5);\n let doubled = $derived(count * 2);\n</script>\n\n<div data-testid=\"number-value\">Number: {count}</div>\n<div data-testid=\"doubled-value\">Doubled: {doubled}</div>\n<button data-testid=\"increment-button\" on:click={() => count++}>\n Increment\n</button>"
}
{
"success": true
}
<script>
let count = $state(5);
let doubled = $derived(count * 2);
</script>
Create a Svelte 5 text analyzer component that uses the `$derived.by` rune for complex derivations.
The component should have a text input field and use `$derived.by` to calculate word count, character count, and whether the text is considered "long" (more than 15 words). Include a clear button to reset the text.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import userEvent from "@testing-library/user-event";
import TextAnalyzer from "./Component.svelte";
describe("TextAnalyzer component", () => {
test("renders with initial state", () => {
render(TextAnalyzer);
expect(screen.getByTestId("word-count")).toHaveTextContent("Words: 0");
expect(screen.getByTestId("char-count")).toHaveTextContent("Characters: 0");
expect(screen.getByTestId("length-indicator")).toHaveTextContent("Status: Short text");
});
test("updates counts when text is entered", async () => {
const user = userEvent.setup();
render(TextAnalyzer);
const input = screen.getByTestId("text-input");
// Enter a short text
await user.type(input, "Hello world");
expect(screen.getByTestId("word-count")).toHaveTextContent("Words: 2");
expect(screen.getByTestId("char-count")).toHaveTextContent("Characters: 11");
expect(screen.getByTestId("length-indicator")).toHaveTextContent("Status: Short text");
// Clear and enter a longer text
await user.clear(input);
await user.type(
input,
"This is a much longer text that should have more than fifteen words so that we can test the long text indicator functionality properly",
);
expect(screen.getByTestId("word-count")).toHaveTextContent("Words: 24");
expect(screen.getByTestId("char-count")).toHaveTextContent("Characters: 134");
expect(screen.getByTestId("length-indicator")).toHaveTextContent("Status: Long text");
});
test("clear button resets the text", async () => {
const user = userEvent.setup();
render(TextAnalyzer);
const input = screen.getByTestId("text-input");
const clearButton = screen.getByTestId("clear-button");
// Enter some text
await user.type(input, "Hello world");
// Verify counts
expect(screen.getByTestId("word-count")).toHaveTextContent("Words: 2");
// Click the clear button
await user.click(clearButton);
// Verify everything is reset
expect(screen.getByTestId("word-count")).toHaveTextContent("Words: 0");
expect(screen.getByTestId("char-count")).toHaveTextContent("Characters: 0");
expect(screen.getByTestId("length-indicator")).toHaveTextContent("Status: Short text");
expect(input).toHaveValue("");
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"code": "<script lang=\"ts\">\n let text = \"\";\n\n const { wordCount, charCount, lengthIndicator } = $derived.by(() => {\n const words = text.trim() === \"\" ? [] : text.trim().split(/\\s+/);\n const charCount = text.length;\n const isLong = words.length > 15;\n \n return {\n wordCount: words.length,\n charCount,\n lengthIndicator: isLong ? \"Long text\" : \"Short text\"\n };\n });\n</script>\n\n<input \n type=\"text\" \n bind:value={text} \n data-testid=\"text-input\" \n placeholder=\"Enter text...\"\n/>\n\n<div data-testid=\"word-count\">Words: {wordCount}</div>\n<div data-testid=\"char-count\">Characters: {charCount}</div>\n<div data-testid=\"length-indicator\">Status: {lengthIndicator}</div>\n\n<button \n data-testid=\"clear-button\" \n on:click={() => { text = \"\"; }}\n>\n Clear\n</button>\n",
"desired_svelte_version": "5",
"async": false,
"filename": "TextAnalyzer.svelte"
}
{
"content": [
{
"type": "text",
"text": "{\"issues\":[\"Using `on:click` to listen to the click event is deprecated. Use the event attribute `onclick` instead\\nhttps://svelte.dev/e/event_directive_deprecated at line 30, column 2\",\"`text` is updated, but is not declared with `$state(...)`. Changing its value will not correctly trigger updates\\nhttps://svelte.dev/e/non_reactive_update at line 2, column 6\"],\"suggestions\":[],\"require_another_tool_call_after_fixing\":true}"
}
],
"isError": false,
"structuredContent": {
"issues": [
"Using `on:click` to listen to the click event is deprecated. Use the event attribute `onclick` instead\nhttps://svelte.dev/e/event_directive_deprecated at line 30, column 2",
"`text` is updated, but is not declared with `$state(...)`. Changing its value will not correctly trigger updates\nhttps://svelte.dev/e/non_reactive_update at line 2, column 6"
],
"suggestions": [],
"require_another_tool_call_after_fixing": true
}
}
{
"async": false,
"code": "<script lang=\"ts\">\n let text = $state(\"\");\n\n const { wordCount, charCount, lengthIndicator } = $derived.by(() => {\n const words = text.trim() === \"\" ? [] : text.trim().split(/\\s+/);\n const charCount = text.length;\n const isLong = words.length > 15;\n \n return {\n wordCount: words.length,\n charCount,\n lengthIndicator: isLong ? \"Long text\" : \"Short text\"\n };\n });\n</script>\n\n<input \n type=\"text\" \n bind:value={text} \n data-testid=\"text-input\" \n placeholder=\"Enter text...\"\n/>\n\n<div data-testid=\"word-count\">Words: {wordCount}</div>\n<div data-testid=\"char-count\">Characters: {charCount}</div>\n<div data-testid=\"length-indicator\">Status: {lengthIndicator}</div>\n\n<button \n data-testid=\"clear-button\" \n onclick={() => { text = \"\"; }}\n>\n Clear\n</button>\n",
"desired_svelte_version": "5",
"filename": "TextAnalyzer.svelte"
}
{
"content": [
{
"type": "text",
"text": "{\"issues\":[],\"suggestions\":[],\"require_another_tool_call_after_fixing\":false}"
}
],
"isError": false,
"structuredContent": {
"issues": [],
"suggestions": [],
"require_another_tool_call_after_fixing": false
}
}
{
"content": "<script lang=\"ts\">\n let text = $state(\"\");\n\n const { wordCount, charCount, lengthIndicator } = $derived.by(() => {\n const words = text.trim() === \"\" ? [] : text.trim().split(/\\s+/);\n const charCount = text.length;\n const isLong = words.length > 15;\n \n return {\n wordCount: words.length,\n charCount,\n lengthIndicator: isLong ? \"Long text\" : \"Short text\"\n };\n });\n</script>\n\n<input \n type=\"text\" \n bind:value={text} \n data-testid=\"text-input\" \n placeholder=\"Enter text...\"\n/>\n\n<div data-testid=\"word-count\">Words: {wordCount}</div>\n<div data-testid=\"char-count\">Characters: {charCount}</div>\n<div data-testid=\"length-indicator\">Status: {lengthIndicator}</div>\n\n<button \n data-testid=\"clear-button\" \n onclick={() => { text = \"\"; }}\n>\n Clear\n</button>\n"
}
{
"success": true,
"message": "All 3 tests passed!",
"passed": 3,
"failed": 0,
"total": 3,
"duration": 1202,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
}
}
{
"content": "<script lang=\"ts\">\n let text = $state(\"\");\n\n const { wordCount, charCount, lengthIndicator } = $derived.by(() => {\n const words = text.trim() === \"\" ? [] : text.trim().split(/\\s+/);\n const charCount = text.length;\n const isLong = words.length > 15;\n \n return {\n wordCount: words.length,\n charCount,\n lengthIndicator: isLong ? \"Long text\" : \"Short text\"\n };\n });\n</script>\n\n<input \n type=\"text\" \n bind:value={text} \n data-testid=\"text-input\" \n placeholder=\"Enter text...\"\n/>\n\n<div data-testid=\"word-count\">Words: {wordCount}</div>\n<div data-testid=\"char-count\">Characters: {charCount}</div>\n<div data-testid=\"length-indicator\">Status: {lengthIndicator}</div>\n\n<button \n data-testid=\"clear-button\" \n onclick={() => { text = \"\"; }}\n>\n Clear\n</button>\n"
}
{
"success": true
}
<script lang="ts">
let text = $state("");
const { wordCount, charCount, lengthIndicator } = $derived.by(() => {
const words = text.trim() === "" ? [] : text.trim().split(/\s+/);Create a Svelte 5 character list component that uses the `{#each}` block.
The component should display a hardcoded list of 3 Seinfeld characters (Jerry, Elaine, Kramer) and include a button to add George to the list.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import userEvent from "@testing-library/user-event";
import CharacterList from "./Component.svelte";
describe("CharacterList component", () => {
test("renders all characters initially", () => {
render(CharacterList);
const characterElements = screen.getAllByTestId("character");
expect(characterElements.length).toBe(3);
expect(characterElements[0]).toHaveTextContent("Jerry");
expect(characterElements[1]).toHaveTextContent("Elaine");
expect(characterElements[2]).toHaveTextContent("Kramer");
});
test("adds George to the list when button clicked", async () => {
const user = userEvent.setup();
render(CharacterList);
// Initial check
let characterElements = screen.getAllByTestId("character");
expect(characterElements.length).toBe(3);
// Click the button to add George
await user.click(screen.getByTestId("add-george-button"));
// Get updated elements
characterElements = screen.getAllByTestId("character");
// Check that George was added
expect(characterElements.length).toBe(4);
expect(characterElements[3]).toHaveTextContent("George");
// Verify original characters are still there
expect(characterElements[0]).toHaveTextContent("Jerry");
expect(characterElements[1]).toHaveTextContent("Elaine");
expect(characterElements[2]).toHaveTextContent("Kramer");
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"content": "<script lang=\"ts\">\n $state characters = [\n { name: 'Jerry', id: 1 },\n { name: 'Elaine', id: 2 },\n { name: 'Kramer', id: 3 }\n ];\n\n function addGeorge() {\n characters = [...characters, { name: 'George', id: 4 }];\n }\n</script>\n\n{#each characters as character (character.id)}\n <div data-testid=\"character\">{character.name}</div>\n{/each}\n\n<button data-testid=\"add-george-button\" on:click={addGeorge}>Add George</button>\n"
}
{
"success": true
}
<script lang="ts">
$state characters = [
{ name: 'Jerry', id: 1 },
{ name: 'Elaine', id: 2 },
{ name: 'Kramer', id: 3 }Create a Svelte 5 number doubler component that uses the `$effect` rune.
The component should have a number input starting at 5, use `$effect` to calculate the doubled value whenever the number changes, and include a button to increment the number.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import userEvent from "@testing-library/user-event";
import NumberDoubler from "./Component.svelte";
describe("NumberDoubler component", () => {
test("renders with initial state", () => {
render(NumberDoubler);
expect(screen.getByTestId("number-value")).toHaveTextContent("Number: 5");
expect(screen.getByTestId("doubled-value")).toHaveTextContent("Doubled: 10");
});
test("updates doubled value when number increments", async () => {
const user = userEvent.setup();
render(NumberDoubler);
await user.click(screen.getByTestId("increment-button"));
expect(screen.getByTestId("number-value")).toHaveTextContent("Number: 6");
expect(screen.getByTestId("doubled-value")).toHaveTextContent("Doubled: 12");
// Click again
await user.click(screen.getByTestId("increment-button"));
expect(screen.getByTestId("number-value")).toHaveTextContent("Number: 7");
expect(screen.getByTestId("doubled-value")).toHaveTextContent("Doubled: 14");
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"content": "<script>\n let number = $state(5);\n\n $effect(() => {\n // This effect runs whenever 'number' changes\n // In Svelte 5, $effect returns a cleanup function\n // For this simple case, we don't need cleanup\n });\n\n function increment() {\n number++;\n }\n</script>\n\n<div>\n <span data-testid=\"number-value\">Number: {number}</span>\n <span data-testid=\"doubled-value\">Doubled: {number * 2}</span>\n <button data-testid=\"increment-button\" on:click={increment}>\n Increment\n </button>\n</div>"
}
{
"success": true
}
<script>
let number = $state(5);
$effect(() => {
// This effect runs whenever 'number' changesCreate a simple Svelte 5 component that displays "Hello, World!" with styling.
The text should be blue, centered, and have a small margin around it.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import HelloWorld from "./Component.svelte"; // Path to the generated component
describe("HelloWorld component", () => {
test("renders with Hello, World! text", () => {
render(HelloWorld);
// Get the greeting element
const greetingElement = screen.getByTestId("greeting");
// Check that it contains the correct text
expect(greetingElement).toHaveTextContent("Hello, World!");
});
test("has the correct styling class", () => {
render(HelloWorld);
// Get the greeting element
const greetingElement = screen.getByTestId("greeting");
// Check that it has the greeting class
expect(greetingElement).toHaveClass("greeting");
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"code": "<script>\n // No special logic needed for this simple component\n</script>\n\n<div class=\"greeting\" data-testid=\"greeting\">\n Hello, World!\n</div>\n\n<style>\n .greeting {\n color: blue;\n text-align: center;\n margin: 1rem;\n }\n</style>",
"desired_svelte_version": "5",
"filename": "Component.svelte"
}
{
"content": [
{
"type": "text",
"text": "{\"issues\":[],\"suggestions\":[],\"require_another_tool_call_after_fixing\":false}"
}
],
"isError": false,
"structuredContent": {
"issues": [],
"suggestions": [],
"require_another_tool_call_after_fixing": false
}
}
{
"content": "<script>\n // No special logic needed for this simple component\n</script>\n\n<div class=\"greeting\" data-testid=\"greeting\">\n Hello, World!\n</div>\n\n<style>\n .greeting {\n color: blue;\n text-align: center;\n margin: 1rem;\n }\n</style>"
}
{
"success": true,
"message": "All 2 tests passed!",
"passed": 2,
"failed": 0,
"total": 2,
"duration": 764
}
{
"content": "<script>\n // No special logic needed for this simple component\n</script>\n\n<div class=\"greeting\" data-testid=\"greeting\">\n Hello, World!\n</div>\n\n<style>\n .greeting {\n color: blue;\n text-align: center;\n margin: 1rem;\n }\n</style>"
}
{
"success": true
}
<script>
// No special logic needed for this simple component
</script>
<div class="greeting" data-testid="greeting">Create a Svelte 5 component that uses the `$inspect` rune to log and track state changes.
The component should have a text input starting with "Hello world", use basic `$inspect` to log the value, implement `$inspect(...).with` to track updates with a custom callback, and use `$inspect.trace()` inside an effect. Display the input value and character count.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe, vi } from "vitest";
import userEvent from "@testing-library/user-event";
import InspectDemo from "./Component.svelte";
// Helper function to check text content with or without quotes
const expectCurrentTextToBe = (element: HTMLElement, expectedText: string) => {
const textContent = element.textContent || "";
const withQuotes = `Current text: "${expectedText}"`;
const withoutQuotes = `Current text: ${expectedText}`;
const hasWithQuotes = textContent.includes(withQuotes);
const hasWithoutQuotes = textContent.includes(withoutQuotes);
expect(hasWithQuotes || hasWithoutQuotes).toBe(true);
if (!hasWithQuotes && !hasWithoutQuotes) {
throw new Error(
`Expected element to contain either "${withQuotes}" or "${withoutQuotes}", but got "${textContent}"`,
);
}
};
// Helper function to get all console output as a single string
const getAllConsoleOutput = (consoleSpy: any) => {
return consoleSpy.mock.calls.map((call: any[]) => call.join(" ")).join("\n");
};
describe("InspectDemo component", () => {
test("renders with initial state", () => {
render(InspectDemo);
// Check initial text value and character count
expectCurrentTextToBe(screen.getByTestId("text-value"), "Hello world");
expect(screen.getByTestId("char-count")).toHaveTextContent("Character count: 11");
});
test("updates text value and character count when input changes", async () => {
const user = userEvent.setup();
// Mock console.log to verify $inspect functionality
const consoleSpy = vi.spyOn(console, "log");
render(InspectDemo);
// Update the input field
const input = screen.getByTestId("text-input");
await user.clear(input);
await user.type(input, "Testing $inspect");
// Check if displayed text updated
expectCurrentTextToBe(screen.getByTestId("text-value"), "Testing $inspect");
// Check if character count updated
expect(screen.getByTestId("char-count")).toHaveTextContent("Character count: 16");
// Verify $inspect features are being used (console.log was called)
// This proves $inspect, $inspect.with, and $inspect.trace are working
expect(consoleSpy).toHaveBeenCalled();
// Verify standard $inspect output is present
const output = getAllConsoleOutput(consoleSpy);
expect(output).toContain("init"); // Basic $inspect always logs init event
expect(output).toContain("update"); // Should have update events from typing
// Restore original console.log
consoleSpy.mockRestore();
});
test("handles special characters correctly", async () => {
const user = userEvent.setup();
const consoleSpy = vi.spyOn(console, "log");
render(InspectDemo);
// Update with special characters
const input = screen.getByTestId("text-input");
await user.clear(input);
await user.type(input, "!@#$%^&*()");
// Check if displayed text updated
expectCurrentTextToBe(screen.getByTestId("text-value"), "!@#$%^&*()");
// Check if character count is correct
expect(screen.getByTestId("char-count")).toHaveTextContent("Character count: 10");
// Verify $inspect features are working
expect(consoleSpy).toHaveBeenCalled();
// Verify standard $inspect output is present
const output = getAllConsoleOutput(consoleSpy);
expect(output).toContain("init"); // Basic $inspect always logs init event
expect(output).toContain("update"); // Should have update events from typing
consoleSpy.mockRestore();
});
test("handles empty input correctly", async () => {
const user = userEvent.setup();
const consoleSpy = vi.spyOn(console, "log");
render(InspectDemo);
// Clear the input
const input = screen.getByTestId("text-input");
await user.clear(input);
// Check if displayed text is empty
expectCurrentTextToBe(screen.getByTestId("text-value"), "");
// Check if character count is zero
expect(screen.getByTestId("char-count")).toHaveTextContent("Character count: 0");
// Verify $inspect features are working
expect(consoleSpy).toHaveBeenCalled();
// Verify standard $inspect output is present
const output = getAllConsoleOutput(consoleSpy);
expect(output).toContain("init"); // Basic $inspect always logs init event
expect(output).toContain("update"); // Should have update events from clearing input
consoleSpy.mockRestore();
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{}
{
"content": [
{
"type": "text",
"text": "List of available Svelte documentation sections with their intended use cases. The \"use_cases\" field describes WHEN each section would be useful - analyze these carefully to determine which sections match the user's query:\n\n- title: Overview, use_cases: project setup, creating new svelte apps, scaffolding, cli tools, initializing projects, path: cli/overview\n- title: Frequently asked questions, use_cases: project setup, initializing new svelte projects, troubleshooting cli installation, package manager configuration, path: cli/faq\n- title: sv create, use_cases: project setup, starting new sveltekit app, initializing project, creating from playground, choosing project template, path: cli/sv-create\n- title: sv add, use_cases: project setup, adding features to existing projects, integrating tools, testing setup, styling setup, authentication, database setup, deployment adapters, path: cli/sv-add\n- title: sv check, use_cases: code quality, ci/cd pipelines, error checking, typescript projects, pre-commit hooks, finding unused css, accessibility auditing, production builds, path: cli/sv-check\n- title: sv migrate, use_cases: migration, upgrading svelte versions, upgrading sveltekit versions, modernizing codebase, svelte 3 to 4, svelte 4 to 5, sveltekit 1 to 2, adopting runes, refactoring deprecated apis, path: cli/sv-migrate\n- title: devtools-json, use_cases: development setup, chrome devtools integration, browser-based editing, local development workflow, debugging setup, path: cli/devtools-json\n- title: drizzle, use_cases: database setup, sql queries, orm integration, data modeling, postgresql, mysql, sqlite, server-side data access, database migrations, type-safe queries, path: cli/drizzle\n- title: eslint, use_cases: code quality, linting, error detection, project setup, code standards, team collaboration, typescript projects, path: cli/eslint\n- title: lucia, use_cases: authentication, login systems, user management, registration pages, session handling, auth setup, path: cli/lucia\n- title: mcp, use_cases: use title and path to estimate use case, path: cli/mcp\n- title: mdsvex, use_cases: blog, content sites, markdown rendering, documentation sites, technical writing, cms integration, article pages, path: cli/mdsvex\n- title: paraglide, use_cases: internationalization, multi-language sites, i18n, translation, localization, language switching, global apps, multilingual content, path: cli/paraglide\n- title: playwright, use_cases: browser testing, e2e testing, integration testing, test automation, quality assurance, ci/cd pipelines, testing user flows, path: cli/playwright\n- title: prettier, use_cases: code formatting, project setup, code style consistency, team collaboration, linting configuration, path: cli/prettier\n- title: storybook, use_cases: component development, design systems, ui library, isolated component testing, documentation, visual testing, component showcase, path: cli/storybook\n- title: sveltekit-adapter, use_cases: deployment, production builds, hosting setup, choosing deployment platform, configuring adapters, static site generation, node server, vercel, cloudflare, netlify, path: cli/sveltekit-adapter\n- title: tailwindcss, use_cases: project setup, styling, css framework, rapid prototyping, utility-first css, design systems, responsive design, adding tailwind to svelte, path: cli/tailwind\n- title: vitest, use_cases: testing, unit tests, component testing, test setup, quality assurance, ci/cd pipelines, test-driven development, path: cli/vitest\n- title: Introduction, use_cases: learning sveltekit, project setup, understanding framework basics, choosing between svelte and sveltekit, getting started with full-stack apps, path: kit/introduction\n- title: Creating a project, use_cases: project setup, starting new sveltekit app, initial development environment, first-time sveltekit users, scaffolding projects, path: kit/creating-a-project\n- title: Project types, use_cases: deployment, project setup, choosing adapters, ssg, spa, ssr, serverless, mobile apps, desktop apps, pwa, offline apps, browser extensions, separate backend, docker containers, path: kit/project-types\n- title: Project structure, use_cases: project setup, understanding file structure, organizing code, starting new project, learning sveltekit basics, path: kit/project-structure\n- title: Web standards, use_cases: always, any sveltekit project, data fetching, forms, api routes, server-side rendering, deployment to various platforms, path: kit/web-standards\n- title: Routing, use_cases: routing, navigation, multi-page apps, project setup, file structure, api endpoints, data loading, layouts, error pages, always, path: kit/routing\n- title: Loading data, use_cases: data fetching, api calls, database queries, dynamic routes, page initialization, loading states, authentication checks, ssr data, form data, content rendering, path: kit/load\n- title: Form actions, use_cases: forms, user input, data submission, authentication, login systems, user registration, progressive enhancement, validation errors, path: kit/form-actions\n- title: Page options, use_cases: prerendering static sites, ssr configuration, spa setup, client-side rendering control, url trailing slash handling, adapter deployment config, build optimization, path: kit/page-options\n- title: State management, use_cases: sveltekit, server-side rendering, ssr, state management, authentication, data persistence, load functions, context api, navigation, component lifecycle, path: kit/state-management\n- title: Remote functions, use_cases: data fetching, server-side logic, database queries, type-safe client-server communication, forms, user input, mutations, authentication, crud operations, optimistic updates, path: kit/remote-functions\n- title: Building your app, use_cases: production builds, deployment preparation, build process optimization, adapter configuration, preview before deployment, path: kit/building-your-app\n- title: Adapters, use_cases: deployment, production builds, hosting setup, choosing deployment platform, configuring adapters, path: kit/adapters\n- title: Zero-config deployments, use_cases: deployment, production builds, hosting setup, choosing deployment platform, ci/cd configuration, path: kit/adapter-auto\n- title: Node servers, use_cases: deployment, production builds, node.js hosting, custom server setup, environment configuration, reverse proxy setup, docker deployment, systemd services, path: kit/adapter-node\n- title: Static site generation, use_cases: static site generation, ssg, prerendering, deployment, github pages, spa mode, blogs, documentation sites, marketing sites, path: kit/adapter-static\n- title: Single-page apps, use_cases: spa mode, single-page apps, client-only rendering, static hosting, mobile app wrappers, no server-side logic, adapter-static setup, fallback pages, path: kit/single-page-apps\n- title: Cloudflare, use_cases: deployment, cloudflare workers, cloudflare pages, hosting setup, production builds, serverless deployment, edge computing, path: kit/adapter-cloudflare\n- title: Cloudflare Workers, use_cases: deploying to cloudflare workers, cloudflare workers sites deployment, legacy cloudflare adapter, wrangler configuration, cloudflare platform bindings, path: kit/adapter-cloudflare-workers\n- title: Netlify, use_cases: deployment, netlify hosting, production builds, serverless functions, edge functions, static site hosting, path: kit/adapter-netlify\n- title: Vercel, use_cases: deployment, vercel hosting, production builds, serverless functions, edge functions, isr, image optimization, environment variables, path: kit/adapter-vercel\n- title: Writing adapters, use_cases: custom deployment, building adapters, unsupported platforms, adapter development, custom hosting environments, path: kit/writing-adapters\n- title: Advanced routing, use_cases: advanced routing, dynamic routes, file viewers, nested paths, custom 404 pages, url validation, route parameters, multi-level navigation, path: kit/advanced-routing\n- title: Hooks, use_cases: authentication, logging, error tracking, request interception, api proxying, custom routing, internationalization, database initialization, middleware logic, session management, path: kit/hooks\n- title: Errors, use_cases: error handling, custom error pages, 404 pages, api error responses, production error logging, error tracking, type-safe errors, path: kit/errors\n- title: Link options, use_cases: routing, navigation, multi-page apps, performance optimization, link preloading, forms with get method, search functionality, focus management, scroll behavior, path: kit/link-options\n- title: Service workers, use_cases: offline support, pwa, caching strategies, performance optimization, precaching assets, network resilience, progressive web apps, path: kit/service-workers\n- title: Server-only modules, use_cases: api keys, environment variables, sensitive data protection, backend security, preventing data leaks, server-side code isolation, path: kit/server-only-modules\n- title: Snapshots, use_cases: forms, user input, preserving form data, multi-step forms, navigation state, preventing data loss, textarea content, input fields, comment systems, surveys, path: kit/snapshots\n- title: Shallow routing, use_cases: modals, dialogs, image galleries, overlays, history-driven ui, mobile-friendly navigation, photo viewers, lightboxes, drawer menus, path: kit/shallow-routing\n- title: Observability, use_cases: performance monitoring, debugging, observability, tracing requests, production diagnostics, analyzing slow requests, finding bottlenecks, monitoring server-side operations, path: kit/observability\n- title: Packaging, use_cases: building component libraries, publishing npm packages, creating reusable svelte components, library development, package distribution, path: kit/packaging\n- title: Auth, use_cases: authentication, login systems, user management, session handling, jwt tokens, protected routes, user credentials, authorization checks, path: kit/auth\n- title: Performance, use_cases: performance optimization, slow loading pages, production deployment, debugging performance issues, reducing bundle size, improving load times, path: kit/performance\n- title: Icons, use_cases: icons, ui components, styling, css frameworks, tailwind, unocss, performance optimization, dependency management, path: kit/icons\n- title: Images, use_cases: image optimization, responsive images, performance, hero images, product photos, galleries, cms integration, cdn setup, asset management, path: kit/images\n- title: Accessibility, use_cases: always, any sveltekit project, screen reader support, keyboard navigation, multi-page apps, client-side routing, internationalization, multilingual sites, path: kit/accessibility\n- title: SEO, use_cases: seo optimization, search engine ranking, content sites, blogs, marketing sites, public-facing apps, sitemaps, amp pages, meta tags, performance optimization, path: kit/seo\n- title: Frequently asked questions, use_cases: troubleshooting package imports, library compatibility issues, client-side code execution, external api integration, middleware setup, database configuration, view transitions, yarn configuration, path: kit/faq\n- title: Integrations, use_cases: project setup, css preprocessors, postcss, scss, sass, less, stylus, typescript setup, adding integrations, tailwind, testing, auth, linting, formatting, path: kit/integrations\n- title: Breakpoint Debugging, use_cases: debugging, breakpoints, development workflow, troubleshooting issues, vscode setup, ide configuration, inspecting code execution, path: kit/debugging\n- title: Migrating to SvelteKit v2, use_cases: migration, upgrading from sveltekit 1 to 2, breaking changes, version updates, path: kit/migrating-to-sveltekit-2\n- title: Migrating from Sapper, use_cases: migrating from sapper, upgrading legacy projects, sapper to sveltekit conversion, project modernization, path: kit/migrating\n- title: Additional resources, use_cases: troubleshooting, getting help, finding examples, learning sveltekit, project templates, common issues, community support, path: kit/additional-resources\n- title: Glossary, use_cases: rendering strategies, performance optimization, deployment configuration, seo requirements, static sites, spas, server-side rendering, prerendering, edge deployment, pwa development, path: kit/glossary\n- title: @sveltejs/kit, use_cases: forms, form actions, server-side validation, form submission, error handling, redirects, json responses, http errors, server utilities, path: kit/@sveltejs-kit\n- title: @sveltejs/kit/hooks, use_cases: middleware, request processing, authentication chains, logging, multiple hooks, request/response transformation, path: kit/@sveltejs-kit-hooks\n- title: @sveltejs/kit/node/polyfills, use_cases: node.js environments, custom servers, non-standard runtimes, ssr setup, web api compatibility, polyfill requirements, path: kit/@sveltejs-kit-node-polyfills\n- title: @sveltejs/kit/node, use_cases: node.js adapter, custom server setup, http integration, streaming files, node deployment, server-side rendering with node, path: kit/@sveltejs-kit-node\n- title: @sveltejs/kit/vite, use_cases: project setup, vite configuration, initial sveltekit setup, build tooling, path: kit/@sveltejs-kit-vite\n- title: $app/environment, use_cases: always, conditional logic, client-side code, server-side code, build-time logic, prerendering, development vs production, environment detection, path: kit/$app-environment\n- title: $app/forms, use_cases: forms, user input, data submission, progressive enhancement, custom form handling, form validation, path: kit/$app-forms\n- title: $app/navigation, use_cases: routing, navigation, multi-page apps, programmatic navigation, data reloading, preloading, shallow routing, navigation lifecycle, scroll handling, view transitions, path: kit/$app-navigation\n- title: $app/paths, use_cases: static assets, images, fonts, public files, base path configuration, subdirectory deployment, cdn setup, asset urls, links, navigation, path: kit/$app-paths\n- title: $app/server, use_cases: remote functions, server-side logic, data fetching, form handling, api endpoints, client-server communication, prerendering, file reading, batch queries, path: kit/$app-server\n- title: $app/state, use_cases: routing, navigation, multi-page apps, loading states, url parameters, form handling, error states, version updates, page metadata, shallow routing, path: kit/$app-state\n- title: $app/stores, use_cases: legacy projects, sveltekit pre-2.12, migration from stores to runes, maintaining older codebases, accessing page data, navigation state, app version updates, path: kit/$app-stores\n- title: $app/types, use_cases: routing, navigation, type safety, route parameters, dynamic routes, link generation, pathname validation, multi-page apps, path: kit/$app-types\n- title: $env/dynamic/private, use_cases: api keys, secrets management, server-side config, environment variables, backend logic, deployment-specific settings, private data handling, path: kit/$env-dynamic-private\n- title: $env/dynamic/public, use_cases: environment variables, client-side config, runtime configuration, public api keys, deployment-specific settings, multi-environment apps, path: kit/$env-dynamic-public\n- title: $env/static/private, use_cases: server-side api keys, backend secrets, database credentials, private configuration, build-time optimization, server endpoints, authentication tokens, path: kit/$env-static-private\n- title: $env/static/public, use_cases: environment variables, public config, client-side data, api endpoints, build-time configuration, public constants, path: kit/$env-static-public\n- title: $lib, use_cases: project setup, component organization, importing shared components, reusable ui elements, code structure, path: kit/$lib\n- title: $service-worker, use_cases: offline support, pwa, service workers, caching strategies, progressive web apps, offline-first apps, path: kit/$service-worker\n- title: Configuration, use_cases: project setup, configuration, adapters, deployment, build settings, environment variables, routing customization, prerendering, csp security, csrf protection, path configuration, typescript setup, path: kit/configuration\n- title: Command Line Interface, use_cases: project setup, typescript configuration, generated types, ./$types imports, initial project configuration, path: kit/cli\n- title: Types, use_cases: typescript, type safety, route parameters, api endpoints, load functions, form actions, generated types, jsconfig setup, path: kit/types\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/overview\n- title: Local setup, use_cases: use title and path to estimate use case, path: mcp/local-setup\n- title: Remote setup, use_cases: use title and path to estimate use case, path: mcp/remote-setup\n- title: Tools, use_cases: use title and path to estimate use case, path: mcp/tools\n- title: Resources, use_cases: use title and path to estimate use case, path: mcp/resources\n- title: Prompts, use_cases: use title and path to estimate use case, path: mcp/prompts\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/plugin\n- title: Skill, use_cases: use title and path to estimate use case, path: mcp/skill\n- title: Subagent, use_cases: use title and path to estimate use case, path: mcp/subagent\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/opencode-plugin\n- title: Subagent, use_cases: use title and path to estimate use case, path: mcp/opencode-subagent\n- title: Overview, use_cases: always, any svelte project, getting started, learning svelte, introduction, project setup, understanding framework basics, path: svelte/overview\n- title: Getting started, use_cases: project setup, starting new svelte project, initial installation, choosing between sveltekit and vite, editor configuration, path: svelte/getting-started\n- title: .svelte files, use_cases: always, any svelte project, component creation, project setup, learning svelte basics, path: svelte/svelte-files\n- title: .svelte.js and .svelte.ts files, use_cases: shared reactive state, reusable reactive logic, state management across components, global stores, custom reactive utilities, path: svelte/svelte-js-files\n- title: What are runes?, use_cases: always, any svelte 5 project, understanding core syntax, learning svelte 5, migration from svelte 4, path: svelte/what-are-runes\n- title: $state, use_cases: always, any svelte project, core reactivity, state management, counters, forms, todo apps, interactive ui, data updates, class-based components, path: svelte/$state\n- title: $derived, use_cases: always, any svelte project, computed values, reactive calculations, derived data, transforming state, dependent values, path: svelte/$derived\n- title: $effect, use_cases: canvas drawing, third-party library integration, dom manipulation, side effects, intervals, timers, network requests, analytics tracking, path: svelte/$effect\n- title: $props, use_cases: always, any svelte project, passing data to components, component communication, reusable components, component props, path: svelte/$props\n- title: $bindable, use_cases: forms, user input, two-way data binding, custom input components, parent-child communication, reusable form fields, path: svelte/$bindable\n- title: $inspect, use_cases: debugging, development, tracking state changes, reactive state monitoring, troubleshooting reactivity issues, path: svelte/$inspect\n- title: $host, use_cases: custom elements, web components, dispatching custom events, component library, framework-agnostic components, path: svelte/$host\n- title: Basic markup, use_cases: always, any svelte project, basic markup, html templating, component structure, attributes, events, props, text rendering, path: svelte/basic-markup\n- title: {#if ...}, use_cases: always, conditional rendering, showing/hiding content, dynamic ui, user permissions, loading states, error handling, form validation, path: svelte/if\n- title: {#each ...}, use_cases: always, lists, arrays, iteration, product listings, todos, tables, grids, dynamic content, shopping carts, user lists, comments, feeds, path: svelte/each\n- title: {#key ...}, use_cases: animations, transitions, component reinitialization, forcing component remount, value-based ui updates, resetting component state, path: svelte/key\n- title: {#await ...}, use_cases: async data fetching, api calls, loading states, promises, error handling, lazy loading components, dynamic imports, path: svelte/await\n- title: {#snippet ...}, use_cases: reusable markup, component composition, passing content to components, table rows, list items, conditional rendering, reducing duplication, path: svelte/snippet\n- title: {@render ...}, use_cases: reusable ui patterns, component composition, conditional rendering, fallback content, layout components, slot alternatives, template reuse, path: svelte/@render\n- title: {@html ...}, use_cases: rendering html strings, cms content, rich text editors, markdown to html, blog posts, wysiwyg output, sanitized html injection, dynamic html content, path: svelte/@html\n- title: {@attach ...}, use_cases: tooltips, popovers, dom manipulation, third-party libraries, canvas drawing, element lifecycle, interactive ui, custom directives, wrapper components, path: svelte/@attach\n- title: {@const ...}, use_cases: computed values in loops, derived calculations in blocks, local variables in each iterations, complex list rendering, path: svelte/@const\n- title: {@debug ...}, use_cases: debugging, development, troubleshooting, tracking state changes, monitoring variables, reactive data inspection, path: svelte/@debug\n- title: bind:, use_cases: forms, user input, two-way data binding, interactive ui, media players, file uploads, checkboxes, radio buttons, select dropdowns, contenteditable, dimension tracking, path: svelte/bind\n- title: use:, use_cases: custom directives, dom manipulation, third-party library integration, tooltips, click outside, gestures, focus management, element lifecycle hooks, path: svelte/use\n- title: transition:, use_cases: animations, interactive ui, modals, dropdowns, notifications, conditional content, show/hide elements, smooth state changes, path: svelte/transition\n- title: in: and out:, use_cases: animation, transitions, interactive ui, conditional rendering, independent enter/exit effects, modals, tooltips, notifications, path: svelte/in-and-out\n- title: animate:, use_cases: sortable lists, drag and drop, reorderable items, todo lists, kanban boards, playlist editors, priority queues, animated list reordering, path: svelte/animate\n- title: style:, use_cases: dynamic styling, conditional styles, theming, dark mode, responsive design, interactive ui, component styling, path: svelte/style\n- title: class, use_cases: always, conditional styling, dynamic classes, tailwind css, component styling, reusable components, responsive design, path: svelte/class\n- title: await, use_cases: async data fetching, loading states, server-side rendering, awaiting promises in components, async validation, concurrent data loading, path: svelte/await-expressions\n- title: Scoped styles, use_cases: always, styling components, scoped css, component-specific styles, preventing style conflicts, animations, keyframes, path: svelte/scoped-styles\n- title: Global styles, use_cases: global styles, third-party libraries, css resets, animations, styling body/html, overriding component styles, shared keyframes, base styles, path: svelte/global-styles\n- title: Custom properties, use_cases: theming, custom styling, reusable components, design systems, dynamic colors, component libraries, ui customization, path: svelte/custom-properties\n- title: Nested <style> elements, use_cases: component styling, scoped styles, dynamic styles, conditional styling, nested style tags, custom styling logic, path: svelte/nested-style-elements\n- title: <svelte:boundary>, use_cases: error handling, async data loading, loading states, error recovery, flaky components, error reporting, resilient ui, path: svelte/svelte-boundary\n- title: <svelte:window>, use_cases: keyboard shortcuts, scroll tracking, window resize handling, responsive layouts, online/offline detection, viewport dimensions, global event listeners, path: svelte/svelte-window\n- title: <svelte:document>, use_cases: document events, visibility tracking, fullscreen detection, pointer lock, focus management, document-level interactions, path: svelte/svelte-document\n- title: <svelte:body>, use_cases: mouse tracking, hover effects, cursor interactions, global body events, drag and drop, custom cursors, interactive backgrounds, body-level actions, path: svelte/svelte-body\n- title: <svelte:head>, use_cases: seo optimization, page titles, meta tags, social media sharing, dynamic head content, multi-page apps, blog posts, product pages, path: svelte/svelte-head\n- title: <svelte:element>, use_cases: dynamic content, cms integration, user-generated content, configurable ui, runtime element selection, flexible components, path: svelte/svelte-element\n- title: <svelte:options>, use_cases: migration, custom elements, web components, legacy mode compatibility, runes mode setup, svg components, mathml components, css injection control, path: svelte/svelte-options\n- title: Stores, use_cases: shared state, cross-component data, reactive values, async data streams, manual control over updates, rxjs integration, extracting logic, path: svelte/stores\n- title: Context, use_cases: shared state, avoiding prop drilling, component communication, theme providers, user context, authentication state, configuration sharing, deeply nested components, path: svelte/context\n- title: Lifecycle hooks, use_cases: component initialization, cleanup tasks, timers, subscriptions, dom measurements, chat windows, autoscroll features, migration from svelte 4, path: svelte/lifecycle-hooks\n- title: Imperative component API, use_cases: project setup, client-side rendering, server-side rendering, ssr, hydration, testing, programmatic component creation, tooltips, dynamic mounting, path: svelte/imperative-component-api\n- title: Hydratable data, use_cases: use title and path to estimate use case, path: svelte/hydratable\n- title: Testing, use_cases: testing, quality assurance, unit tests, integration tests, component tests, e2e tests, vitest setup, playwright setup, test automation, path: svelte/testing\n- title: TypeScript, use_cases: typescript setup, type safety, component props typing, generic components, wrapper components, dom type augmentation, project configuration, path: svelte/typescript\n- title: Custom elements, use_cases: web components, custom elements, component library, design system, framework-agnostic components, embedding svelte in non-svelte apps, shadow dom, path: svelte/custom-elements\n- title: Svelte 4 migration guide, use_cases: upgrading svelte 3 to 4, version migration, updating dependencies, breaking changes, legacy project maintenance, path: svelte/v4-migration-guide\n- title: Svelte 5 migration guide, use_cases: migrating from svelte 4 to 5, upgrading projects, learning svelte 5 syntax changes, runes migration, event handler updates, path: svelte/v5-migration-guide\n- title: Frequently asked questions, use_cases: getting started, learning svelte, beginner setup, project initialization, vs code setup, formatting, testing, routing, mobile apps, troubleshooting, community support, path: svelte/faq\n- title: svelte, use_cases: migration from svelte 4 to 5, upgrading legacy code, component lifecycle hooks, context api, mounting components, event dispatchers, typescript component types, path: svelte/svelte\n- title: svelte/action, use_cases: typescript types, actions, use directive, dom manipulation, element lifecycle, custom behaviors, third-party library integration, path: svelte/svelte-action\n- title: svelte/animate, use_cases: animated lists, sortable items, drag and drop, reordering elements, todo lists, kanban boards, playlist management, smooth position transitions, path: svelte/svelte-animate\n- title: svelte/attachments, use_cases: library development, component libraries, programmatic element manipulation, migrating from actions to attachments, spreading props onto elements, path: svelte/svelte-attachments\n- title: svelte/compiler, use_cases: build tools, custom compilers, ast manipulation, preprocessors, code transformation, migration scripts, syntax analysis, bundler plugins, dev tools, path: svelte/svelte-compiler\n- title: svelte/easing, use_cases: animations, transitions, custom easing, smooth motion, interactive ui, modals, dropdowns, carousels, page transitions, scroll effects, path: svelte/svelte-easing\n- title: svelte/events, use_cases: window events, document events, global event listeners, event delegation, programmatic event handling, cleanup functions, media queries, path: svelte/svelte-events\n- title: svelte/legacy, use_cases: migration from svelte 4 to svelte 5, upgrading legacy code, event modifiers, class components, imperative component instantiation, path: svelte/svelte-legacy\n- title: svelte/motion, use_cases: animation, smooth transitions, interactive ui, sliders, counters, physics-based motion, drag gestures, accessibility, reduced motion, path: svelte/svelte-motion\n- title: svelte/reactivity/window, use_cases: responsive design, viewport tracking, scroll effects, window resize handling, online/offline detection, zoom level tracking, path: svelte/svelte-reactivity-window\n- title: svelte/reactivity, use_cases: reactive data structures, state management with maps/sets, game boards, selection tracking, url manipulation, query params, real-time clocks, media queries, responsive design, path: svelte/svelte-reactivity\n- title: svelte/server, use_cases: server-side rendering, ssr, static site generation, seo optimization, initial page load, pre-rendering, node.js server, custom server setup, path: svelte/svelte-server\n- title: svelte/store, use_cases: state management, shared data, reactive stores, cross-component communication, global state, computed values, data synchronization, legacy svelte projects, path: svelte/svelte-store\n- title: svelte/transition, use_cases: animations, transitions, interactive ui, modals, dropdowns, tooltips, notifications, svg animations, list animations, page transitions, path: svelte/svelte-transition\n- title: Compiler errors, use_cases: animation, transitions, keyed each blocks, list animations, path: svelte/compiler-errors\n- title: Compiler warnings, use_cases: accessibility, a11y compliance, wcag standards, screen readers, keyboard navigation, aria attributes, semantic html, interactive elements, path: svelte/compiler-warnings\n- title: Runtime errors, use_cases: debugging errors, error handling, troubleshooting runtime issues, migration to svelte 5, component binding, effects and reactivity, path: svelte/runtime-errors\n- title: Runtime warnings, use_cases: debugging state proxies, console logging reactive values, inspecting state changes, development troubleshooting, path: svelte/runtime-warnings\n- title: Overview, use_cases: migrating from svelte 3/4 to svelte 5, maintaining legacy components, understanding deprecated features, gradual upgrade process, path: svelte/legacy-overview\n- title: Reactive let/var declarations, use_cases: migration, legacy svelte projects, upgrading from svelte 4, understanding old reactivity, maintaining existing code, learning runes differences, path: svelte/legacy-let\n- title: Reactive $: statements, use_cases: legacy mode, migration from svelte 4, reactive statements, computed values, derived state, side effects, path: svelte/legacy-reactive-assignments\n- title: export let, use_cases: legacy mode, migration from svelte 4, maintaining older projects, component props without runes, exporting component methods, renaming reserved word props, path: svelte/legacy-export-let\n- title: $$props and $$restProps, use_cases: legacy mode migration, component wrappers, prop forwarding, button components, reusable ui components, spreading props to child elements, path: svelte/legacy-$$props-and-$$restProps\n- title: on:, use_cases: legacy mode, event handling, button clicks, forms, user interactions, component communication, event forwarding, event modifiers, path: svelte/legacy-on\n- title: <slot>, use_cases: legacy mode, migrating from svelte 4, component composition, reusable components, passing content to components, modals, layouts, wrappers, path: svelte/legacy-slots\n- title: $$slots, use_cases: legacy mode, conditional slot rendering, optional content sections, checking if slots provided, migrating from legacy to runes, path: svelte/legacy-$$slots\n- title: <svelte:fragment>, use_cases: named slots, component composition, layout systems, avoiding wrapper divs, legacy svelte projects, slot content organization, path: svelte/legacy-svelte-fragment\n- title: <svelte:component>, use_cases: dynamic components, component switching, conditional rendering, legacy mode migration, tabbed interfaces, multi-step forms, path: svelte/legacy-svelte-component\n- title: <svelte:self>, use_cases: recursive components, tree structures, nested menus, file explorers, comment threads, hierarchical data, path: svelte/legacy-svelte-self\n- title: Imperative component API, use_cases: migration from svelte 3/4 to 5, legacy component api, maintaining old projects, understanding deprecated patterns, path: svelte/legacy-component-api\n\nCarefully analyze the use_cases field for each section to identify which documentation is relevant for the user's specific query. The use_cases contain keywords for project types, features, components, and development stages. After identifying relevant sections, use the get-documentation tool with ALL relevant section titles or paths at once (can pass multiple sections as an array)."
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{
"section": "[\"$inspect\", \"$state\", \"$effect\"]"
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"text": "## $inspect\n\n> [!NOTE] `$inspect` only works during development. In a production build it becomes a noop.\n\nThe `$inspect` rune is roughly equivalent to `console.log`, with the exception that it will re-run whenever its argument changes. `$inspect` tracks reactive state deeply, meaning that updating something inside an object or array using fine-grained reactivity will cause it to re-fire ([demo](/playground/untitled#H4sIAAAAAAAACkWQ0YqDQAxFfyUMhSotdZ-tCvu431AXtGOqQ2NmmMm0LOK_r7Utfby5JzeXTOpiCIPKT5PidkSVq2_n1F7Jn3uIcEMSXHSw0evHpAjaGydVzbUQCmgbWaCETZBWMPlKj29nxBDaHj_edkAiu12JhdkYDg61JGvE_s2nR8gyuBuiJZuDJTyQ7eE-IEOzog1YD80Lb0APLfdYc5F9qnFxjiKWwbImo6_llKRQVs-2u91c_bD2OCJLkT3JZasw7KLA2XCX31qKWE6vIzNk1fKE0XbmYrBTufiI8-_8D2cUWBA_AQAA)):\n\n```svelte\n<script>\n\tlet count = $state(0);\n\tlet message = $state('hello');\n\n\t$inspect(count, message); // will console.log when `count` or `message` change\n</script>\n\n<button onclick={() => count++}>Increment</button>\n<input bind:value={message} />\n```\n\nOn updates, a stack trace will be printed, making it easy to find the origin of a state change (unless you're in the playground, due to technical limitations).\n\n## $inspect(...).with\n\n`$inspect` returns a property `with`, which you can invoke with a callback, which will then be invoked instead of `console.log`. The first argument to the callback is either `\"init\"` or `\"update\"`; subsequent arguments are the values passed to `$inspect` ([demo](/playground/untitled#H4sIAAAAAAAACkVQ24qDMBD9lSEUqlTqPlsj7ON-w7pQG8c2VCchmVSK-O-bKMs-DefKYRYx6BG9qL4XQd2EohKf1opC8Nsm4F84MkbsTXAqMbVXTltuWmp5RAZlAjFIOHjuGLOP_BKVqB00eYuKs82Qn2fNjyxLtcWeyUE2sCRry3qATQIpJRyD7WPVMf9TW-7xFu53dBcoSzAOrsqQNyOe2XUKr0Xi5kcMvdDB2wSYO-I9vKazplV1-T-d6ltgNgSG1KjVUy7ZtmdbdjqtzRcphxMS1-XubOITJtPrQWMvKnYB15_1F7KKadA_AQAA)):\n\n```svelte\n<script>\n\tlet count = $state(0);\n\n\t$inspect(count).with((type, count) => {\n\t\tif (type === 'update') {\n\t\t\tdebugger; // or `console.trace`, or whatever you want\n\t\t}\n\t});\n</script>\n\n<button onclick={() => count++}>Increment</button>\n```\n\n## $inspect.trace(...)\n\nThis rune, added in 5.14, causes the surrounding function to be _traced_ in development. Any time the function re-runs as part of an [effect]($effect) or a [derived]($derived), information will be printed to the console about which pieces of reactive state caused the effect to fire.\n\n```svelte\n<script>\n\timport { doSomeWork } from './elsewhere';\n\n\t$effect(() => {\n\t\t+++// $inspect.trace must be the first statement of a function body+++\n\t\t+++$inspect.trace();+++\n\t\tdoSomeWork();\n\t});\n</script>\n```\n\n`$inspect.trace` takes an optional first argument which will be used as the label.\n\n---\n\n## $state\n\nThe `$state` rune allows you to create _reactive state_, which means that your UI _reacts_ when it changes.\n\n```svelte\n<script>\n\tlet count = $state(0);\n</script>\n\n<button onclick={() => count++}>\n\tclicks: {count}\n</button>\n```\n\nUnlike other frameworks you may have encountered, there is no API for interacting with state — `count` is just a number, rather than an object or a function, and you can update it like you would update any other variable.\n\n### Deep state\n\nIf `$state` is used with an array or a simple object, the result is a deeply reactive _state proxy_. [Proxies](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy) allow Svelte to run code when you read or write properties, including via methods like `array.push(...)`, triggering granular updates.\n\nState is proxified recursively until Svelte finds something other than an array or simple object (like a class or an object created with `Object.create`). In a case like this...\n\n```js\nlet todos = $state([\n\t{\n\t\tdone: false,\n\t\ttext: 'add more todos'\n\t}\n]);\n```\n\n...modifying an individual todo's property will trigger updates to anything in your UI that depends on that specific property:\n\n```js\nlet todos = [{ done: false, text: 'add more todos' }];\n// ---cut---\ntodos[0].done = !todos[0].done;\n```\n\nIf you push a new object to the array, it will also be proxified:\n\n```js\nlet todos = [{ done: false, text: 'add more todos' }];\n// ---cut---\ntodos.push({\n\tdone: false,\n\ttext: 'eat lunch'\n});\n```\n\n> [!NOTE] When you update properties of proxies, the original object is _not_ mutated. If you need to use your own proxy handlers in a state proxy, [you should wrap the object _after_ wrapping it in `$state`](https://svelte.dev/playground/hello-world?version=latest#H4sIAAAAAAAACpWR3WoDIRCFX2UqhWyIJL3erAulL9C7XnQLMe5ksbUqOpsfln33YuyGFNJC8UKdc2bOhw7Myk9kJXsJ0nttO9jcR5KEG9AWJDwHdzwxznbaYGTl68Do5JM_FRifuh-9X8Y9Gkq1rYx4q66cJbQUWcmqqIL2VDe2IYMEbvuOikBADi-GJDSkXG-phId0G-frye2DO2psQYDFQ0Ys8gQO350dUkEydEg82T0GOs0nsSG9g2IqgxACZueo2ZUlpdvoDC6N64qsg1QKY8T2bpZp8gpIfbCQ85Zn50Ud82HkeY83uDjspenxv3jXcSDyjPWf9L1vJf0GH666J-jLu1ery4dV257IWXBWGa0-xFDMQdTTn2ScxWKsn86ROsLwQxqrVR5QM84Ij8TKFD2-cUZSm4O2LSt30kQcvwCgCmfZnAIAAA==).\n\nNote that if you destructure a reactive value, the references are not reactive — as in normal JavaScript, they are evaluated at the point of destructuring:\n\n```js\nlet todos = [{ done: false, text: 'add more todos' }];\n// ---cut---\nlet { done, text } = todos[0];\n\n// this will not affect the value of `done`\ntodos[0].done = !todos[0].done;\n```\n\n### Classes\n\nClass instances are not proxied. Instead, you can use `$state` in class fields (whether public or private), or as the first assignment to a property immediately inside the `constructor`:\n\n```js\n// @errors: 7006 2554\nclass Todo {\n\tdone = $state(false);\n\n\tconstructor(text) {\n\t\tthis.text = $state(text);\n\t}\n\n\treset() {\n\t\tthis.text = '';\n\t\tthis.done = false;\n\t}\n}\n```\n\n> [!NOTE] The compiler transforms `done` and `text` into `get`/`set` methods on the class prototype referencing private fields. This means the properties are not enumerable.\n\nWhen calling methods in JavaScript, the value of [`this`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this) matters. This won't work, because `this` inside the `reset` method will be the `<button>` rather than the `Todo`:\n\n```svelte\n<button onclick={todo.reset}>\n\treset\n</button>\n```\n\nYou can either use an inline function...\n\n```svelte\n<button onclick=+++{() => todo.reset()}>+++\n\treset\n</button>\n```\n\n...or use an arrow function in the class definition:\n\n```js\n// @errors: 7006 2554\nclass Todo {\n\tdone = $state(false);\n\n\tconstructor(text) {\n\t\tthis.text = $state(text);\n\t}\n\n\t+++reset = () => {+++\n\t\tthis.text = '';\n\t\tthis.done = false;\n\t}\n}\n```\n\n### Built-in classes\n\nSvelte provides reactive implementations of built-in classes like `Set`, `Map`, `Date` and `URL` that can be imported from [`svelte/reactivity`](svelte-reactivity).\n\n## `$state.raw`\n\nIn cases where you don't want objects and arrays to be deeply reactive you can use `$state.raw`.\n\nState declared with `$state.raw` cannot be mutated; it can only be _reassigned_. In other words, rather than assigning to a property of an object, or using an array method like `push`, replace the object or array altogether if you'd like to update it:\n\n```js\nlet person = $state.raw({\n\tname: 'Heraclitus',\n\tage: 49\n});\n\n// this will have no effect\nperson.age += 1;\n\n// this will work, because we're creating a new person\nperson = {\n\tname: 'Heraclitus',\n\tage: 50\n};\n```\n\nThis can improve performance with large arrays and objects that you weren't planning to mutate anyway, since it avoids the cost of making them reactive. Note that raw state can _contain_ reactive state (for example, a raw array of reactive objects).\n\nAs with `$state`, you can declare class fields using `$state.raw`.\n\n## `$state.snapshot`\n\nTo take a static snapshot of a deeply reactive `$state` proxy, use `$state.snapshot`:\n\n```svelte\n<script>\n\tlet counter = $state({ count: 0 });\n\n\tfunction onclick() {\n\t\t// Will log `{ count: ... }` rather than `Proxy { ... }`\n\t\tconsole.log($state.snapshot(counter));\n\t}\n</script>\n```\n\nThis is handy when you want to pass some state to an external library or API that doesn't expect a proxy, such as `structuredClone`.\n\n## `$state.eager`\n\nWhen state changes, it may not be reflected in the UI immediately if it is used by an `await` expression, because [updates are synchronized](await-expressions#Synchronized-updates).\n\nIn some cases, you may want to update the UI as soon as the state changes. For example, you might want to update a navigation bar when the user clicks on a link, so that they get visual feedback while waiting for the new page to load. To do this, use `$state.eager(value)`:\n\n```svelte\n<nav>\n\t<a href=\"/\" aria-current={$state.eager(pathname) === '/' ? 'page' : null}>home</a>\n\t<a href=\"/about\" aria-current={$state.eager(pathname) === '/about' ? 'page' : null}>about</a>\n</nav>\n```\n\nUse this feature sparingly, and only to provide feedback in response to user action — in general, allowing Svelte to coordinate updates will provide a better user experience.\n\n## Passing state into functions\n\nJavaScript is a _pass-by-value_ language — when you call a function, the arguments are the _values_ rather than the _variables_. In other words:\n\n```js\n/// file: index.js\n// @filename: index.js\n// ---cut---\n/**\n * @param {number} a\n * @param {number} b\n */\nfunction add(a, b) {\n\treturn a + b;\n}\n\nlet a = 1;\nlet b = 2;\nlet total = add(a, b);\nconsole.log(total); // 3\n\na = 3;\nb = 4;\nconsole.log(total); // still 3!\n```\n\nIf `add` wanted to have access to the _current_ values of `a` and `b`, and to return the current `total` value, you would need to use functions instead:\n\n```js\n/// file: index.js\n// @filename: index.js\n// ---cut---\n/**\n * @param {() => number} getA\n * @param {() => number} getB\n */\nfunction add(+++getA, getB+++) {\n\treturn +++() => getA() + getB()+++;\n}\n\nlet a = 1;\nlet b = 2;\nlet total = add+++(() => a, () => b)+++;\nconsole.log(+++total()+++); // 3\n\na = 3;\nb = 4;\nconsole.log(+++total()+++); // 7\n```\n\nState in Svelte is no different — when you reference something declared with the `$state` rune...\n\n```js\nlet a = +++$state(1)+++;\nlet b = +++$state(2)+++;\n```\n\n...you're accessing its _current value_.\n\nNote that 'functions' is broad — it encompasses properties of proxies and [`get`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/get)/[`set`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/set) properties...\n\n```js\n/// file: index.js\n// @filename: index.js\n// ---cut---\n/**\n * @param {{ a: number, b: number }} input\n */\nfunction add(input) {\n\treturn {\n\t\tget value() {\n\t\t\treturn input.a + input.b;\n\t\t}\n\t};\n}\n\nlet input = $state({ a: 1, b: 2 });\nlet total = add(input);\nconsole.log(total.value); // 3\n\ninput.a = 3;\ninput.b = 4;\nconsole.log(total.value); // 7\n```\n\n...though if you find yourself writing code like that, consider using [classes](#Classes) instead.\n\n## Passing state across modules\n\nYou can declare state in `.svelte.js` and `.svelte.ts` files, but you can only _export_ that state if it's not directly reassigned. In other words you can't do this:\n\n```js\n/// file: state.svelte.js\nexport let count = $state(0);\n\nexport function increment() {\n\tcount += 1;\n}\n```\n\nThat's because every reference to `count` is transformed by the Svelte compiler — the code above is roughly equivalent to this:\n\n```js\n/// file: state.svelte.js (compiler output)\n// @filename: index.ts\ninterface Signal<T> {\n\tvalue: T;\n}\n\ninterface Svelte {\n\tstate<T>(value?: T): Signal<T>;\n\tget<T>(source: Signal<T>): T;\n\tset<T>(source: Signal<T>, value: T): void;\n}\ndeclare const $: Svelte;\n// ---cut---\nexport let count = $.state(0);\n\nexport function increment() {\n\t$.set(count, $.get(count) + 1);\n}\n```\n\n> [!NOTE] You can see the code Svelte generates by clicking the 'JS Output' tab in the [playground](/playground).\n\nSince the compiler only operates on one file at a time, if another file imports `count` Svelte doesn't know that it needs to wrap each reference in `$.get` and `$.set`:\n\n```js\n// @filename: state.svelte.js\nexport let count = 0;\n\n// @filename: index.js\n// ---cut---\nimport { count } from './state.svelte.js';\n\nconsole.log(typeof count); // 'object', not 'number'\n```\n\nThis leaves you with two options for sharing state between modules — either don't reassign it...\n\n```js\n// This is allowed — since we're updating\n// `counter.count` rather than `counter`,\n// Svelte doesn't wrap it in `$.state`\nexport const counter = $state({\n\tcount: 0\n});\n\nexport function increment() {\n\tcounter.count += 1;\n}\n```\n\n...or don't directly export it:\n\n```js\nlet count = $state(0);\n\nexport function getCount() {\n\treturn count;\n}\n\nexport function increment() {\n\tcount += 1;\n}\n```\n\n---\n\n## $effect\n\nEffects are functions that run when state updates, and can be used for things like calling third-party libraries, drawing on `<canvas>` elements, or making network requests. They only run in the browser, not during server-side rendering.\n\nGenerally speaking, you should _not_ update state inside effects, as it will make code more convoluted and will often lead to never-ending update cycles. If you find yourself doing so, see [when not to use `$effect`](#When-not-to-use-$effect) to learn about alternative approaches.\n\nYou can create an effect with the `$effect` rune ([demo](/playground/untitled#H4sIAAAAAAAAE31S246bMBD9lZF3pSRSAqTVvrCAVPUP2sdSKY4ZwJJjkD0hSVH-vbINuWxXfQH5zMyZc2ZmZLVUaFn6a2R06ZGlHmBrpvnBvb71fWQHVOSwPbf4GS46TajJspRlVhjZU1HqkhQSWPkHIYdXS5xw-Zas3ueI6FRn7qHFS11_xSRZhIxbFtcDtw7SJb1iXaOg5XIFeQGjzyPRaevYNOGZIJ8qogbpe8CWiy_VzEpTXiQUcvPDkSVrSNZz1UlW1N5eLcqmpdXUvaQ4BmqlhZNUCgxuzFHDqUWNAxrYeUM76AzsnOsdiJbrBp_71lKpn3RRbii-4P3f-IMsRxS-wcDV_bL4PmSdBa2wl7pKnbp8DMgVvJm8ZNskKRkEM_OzyOKQFkgqOYBQ3Nq89Ns0nbIl81vMFN-jKoLMTOr-SOBOJS-Z8f5Y6D1wdcR8dFqvEBdetK-PHwj-z-cH8oHPY54wRJ8Ys7iSQ3Bg3VA9azQbmC9k35kKzYa6PoVtfwbbKVnBixBiGn7Pq0rqJoUtHiCZwAM3jdTPWCVtr_glhVrhecIa3vuksJ_b7TqFs4DPyriSjd5IwoNNQaAmNI-ESfR2p8zimzvN1swdCkvJHPH6-_oX8o1SgcIDAAA=)):\n\n```svelte\n<script>\n\tlet size = $state(50);\n\tlet color = $state('#ff3e00');\n\n\tlet canvas;\n\n\t$effect(() => {\n\t\tconst context = canvas.getContext('2d');\n\t\tcontext.clearRect(0, 0, canvas.width, canvas.height);\n\n\t\t// this will re-run whenever `color` or `size` change\n\t\tcontext.fillStyle = color;\n\t\tcontext.fillRect(0, 0, size, size);\n\t});\n</script>\n\n<canvas bind:this={canvas} width=\"100\" height=\"100\"></canvas>\n```\n\nWhen Svelte runs an effect function, it tracks which pieces of state (and derived state) are accessed (unless accessed inside [`untrack`](svelte#untrack)), and re-runs the function when that state later changes.\n\n> [!NOTE] If you're having difficulty understanding why your `$effect` is rerunning or is not running see [understanding dependencies](#Understanding-dependencies). Effects are triggered differently than the `$:` blocks you may be used to if coming from Svelte 4.\n\n### Understanding lifecycle\n\nYour effects run after the component has been mounted to the DOM, and in a [microtask](https://developer.mozilla.org/en-US/docs/Web/API/HTML_DOM_API/Microtask_guide) after state changes. Re-runs are batched (i.e. changing `color` and `size` in the same moment won't cause two separate runs), and happen after any DOM updates have been applied.\n\nYou can use `$effect` anywhere, not just at the top level of a component, as long as it is called while a parent effect is running.\n\n> [!NOTE] Svelte uses effects internally to represent logic and expressions in your template — this is how `<h1>hello {name}!</h1>` updates when `name` changes.\n\nAn effect can return a _teardown function_ which will run immediately before the effect re-runs ([demo](/playground/untitled#H4sIAAAAAAAAE42SQVODMBCF_8pOxkPRKq3HCsx49K4n64xpskjGkDDJ0tph-O8uINo6HjxB3u7HvrehE07WKDbiyZEhi1osRWksRrF57gQdm6E2CKx_dd43zU3co6VB28mIf-nKO0JH_BmRRRVMQ8XWbXkAgfKtI8jhIpIkXKySu7lSG2tNRGZ1_GlYr1ZTD3ddYFmiosUigbyAbpC2lKbwWJkIB8ZhhxBQBWRSw6FCh3sM8GrYTthL-wqqku4N44TyqEgwF3lmRHr4Op0PGXoH31c5rO8mqV-eOZ49bikgtcHBL55tmhIkEMqg_cFB2TpFxjtg703we6NRL8HQFCS07oSUCZi6Rm04lz1yytIHBKoQpo1w6Gsm4gmyS8b8Y5PydeMdX8gwS2Ok4I-ov5NZtvQde95GMsccn_1wzNKfu3RZtS66cSl9lvL7qO1aIk7knbJGvefdtIOzi73M4bYvovUHDFk6AcX_0HRESxnpBOW_jfCDxIZCi_1L_wm4xGQ60wIAAA==)).\n\n```svelte\n<script>\n\tlet count = $state(0);\n\tlet milliseconds = $state(1000);\n\n\t$effect(() => {\n\t\t// This will be recreated whenever `milliseconds` changes\n\t\tconst interval = setInterval(() => {\n\t\t\tcount += 1;\n\t\t}, milliseconds);\n\n\t\treturn () => {\n\t\t\t// if a teardown function is provided, it will run\n\t\t\t// a) immediately before the effect re-runs\n\t\t\t// b) when the component is destroyed\n\t\t\tclearInterval(interval);\n\t\t};\n\t});\n</script>\n\n<h1>{count}</h1>\n\n<button onclick={() => (milliseconds *= 2)}>slower</button>\n<button onclick={() => (milliseconds /= 2)}>faster</button>\n```\n\nTeardown functions also run when the effect is destroyed, which happens when its parent is destroyed (for example, a component is unmounted) or the parent effect re-runs.\n\n### Understanding dependencies\n\n`$effect` automatically picks up any reactive values (`$state`, `$derived`, `$props`) that are _synchronously_ read inside its function body (including indirectly, via function calls) and registers them as dependencies. When those dependencies change, the `$effect` schedules a re-run.\n\nIf `$state` and `$derived` are used directly inside the `$effect` (for example, during creation of a [reactive class](https://svelte.dev/docs/svelte/$state#Classes)), those values will _not_ be treated as dependencies.\n\nValues that are read _asynchronously_ — after an `await` or inside a `setTimeout`, for example — will not be tracked. Here, the canvas will be repainted when `color` changes, but not when `size` changes ([demo](/playground/untitled#H4sIAAAAAAAAE31T246bMBD9lZF3pWSlBEirfaEQqdo_2PatVIpjBrDkGGQPJGnEv1e2IZfVal-wfHzmzJyZ4cIqqdCy9M-F0blDlnqArZjmB3f72XWRHVCRw_bc4me4aDWhJstSlllhZEfbQhekkMDKfwg5PFvihMvX5OXH_CJa1Zrb0-Kpqr5jkiwC48rieuDWQbqgZ6wqFLRcvkC-hYvnkWi1dWqa8ESQTxFRjfQWsOXiWzmr0sSLhEJu3p1YsoJkNUcdZUnN9dagrBu6FVRQHAM10sJRKgUG16bXcGxQ44AGdt7SDkTDdY02iqLHnJVU6hedlWuIp94JW6Tf8oBt_8GdTxlF0b4n0C35ZLBzXb3mmYn3ae6cOW74zj0YVzDNYXRHFt9mprNgHfZSl6mzml8CMoLvTV6wTZIUDEJv5us2iwMtiJRyAKG4tXnhl8O0yhbML0Wm-B7VNlSSSd31BG7z8oIZZ6dgIffAVY_5xdU9Qrz1Bnx8fCfwtZ7v8Qc9j3nB8PqgmMWlHIID6-bkVaPZwDySfWtKNGtquxQ23Qlsq2QJT0KIqb8dL0up6xQ2eIBkAg_c1FI_YqW0neLnFCqFpwmreedJYT7XX8FVOBfwWRhXstZrSXiwKQjUhOZeMIleb5JZfHWn2Yq5pWEpmR7Hv-N_wEqT8hEEAAA=)):\n\n```ts\n// @filename: index.ts\ndeclare let canvas: {\n\twidth: number;\n\theight: number;\n\tgetContext(type: '2d', options?: CanvasRenderingContext2DSettings): CanvasRenderingContext2D;\n};\ndeclare let color: string;\ndeclare let size: number;\n\n// ---cut---\n$effect(() => {\n\tconst context = canvas.getContext('2d');\n\tcontext.clearRect(0, 0, canvas.width, canvas.height);\n\n\t// this will re-run whenever `color` changes...\n\tcontext.fillStyle = color;\n\n\tsetTimeout(() => {\n\t\t// ...but not when `size` changes\n\t\tcontext.fillRect(0, 0, size, size);\n\t}, 0);\n});\n```\n\nAn effect only reruns when the object it reads changes, not when a property inside it changes. (If you want to observe changes _inside_ an object at dev time, you can use [`$inspect`]($inspect).)\n\n```svelte\n<script>\n\tlet state = $state({ value: 0 });\n\tlet derived = $derived({ value: state.value * 2 });\n\n\t// this will run once, because `state` is never reassigned (only mutated)\n\t$effect(() => {\n\t\tstate;\n\t});\n\n\t// this will run whenever `state.value` changes...\n\t$effect(() => {\n\t\tstate.value;\n\t});\n\n\t// ...and so will this, because `derived` is a new object each time\n\t$effect(() => {\n\t\tderived;\n\t});\n</script>\n\n<button onclick={() => (state.value += 1)}>\n\t{state.value}\n</button>\n\n<p>{state.value} doubled is {derived.value}</p>\n```\n\nAn effect only depends on the values that it read the last time it ran. This has interesting implications for effects that have conditional code.\n\nFor instance, if `condition` is `true` in the code snippet below, the code inside the `if` block will run and `color` will be evaluated. This means that changes to either `condition` or `color` [will cause the effect to re-run](/playground/untitled#H4sIAAAAAAAAE21RQW6DMBD8ytaNBJHaJFLViwNIVZ8RcnBgXVk1xsILTYT4e20TQg89IOPZ2fHM7siMaJBx9tmaWpFqjQNlAKXEihx7YVJpdIyfRkY3G4gB8Pi97cPanRtQU8AuwuF_eNUaQuPlOMtc1SlLRWlKUo1tOwJflUikQHZtA0klzCDc64Imx0ANn8bInV1CDhtHgjClrsftcSXotluLybOUb3g4JJHhOZs5WZpuIS9gjNqkJKQP5e2ClrR4SMdZ13E4xZ8zTPOTJU2A2uE_PQ9COCI926_hTVarIU4hu_REPlBrKq2q73ycrf1N-vS4TMUsulaVg3EtR8H9rFgsg8uUsT1B2F9eshigZHBRpuaD0D3mY8Qm2BfB5N2YyRzdNEYVDy0Ja-WsFjcOUuP1HvFLWA6H3XuHTUSmmDV2--0TXonxsKbp7G9C6R__NONS-MFNvxj_d6mBAgAA).\n\nConversely, if `condition` is `false`, `color` will not be evaluated, and the effect will _only_ re-run again when `condition` changes.\n\n```ts\n// @filename: ambient.d.ts\ndeclare module 'canvas-confetti' {\n\tinterface ConfettiOptions {\n\t\tcolors: string[];\n\t}\n\n\tfunction confetti(opts?: ConfettiOptions): void;\n\texport default confetti;\n}\n\n// @filename: index.js\n// ---cut---\nimport confetti from 'canvas-confetti';\n\nlet condition = $state(true);\nlet color = $state('#ff3e00');\n\n$effect(() => {\n\tif (condition) {\n\t\tconfetti({ colors: [color] });\n\t} else {\n\t\tconfetti();\n\t}\n});\n```\n\n## `$effect.pre`\n\nIn rare cases, you may need to run code _before_ the DOM updates. For this we can use the `$effect.pre` rune:\n\n```svelte\n<script>\n\timport { tick } from 'svelte';\n\n\tlet div = $state();\n\tlet messages = $state([]);\n\n\t// ...\n\n\t$effect.pre(() => {\n\t\tif (!div) return; // not yet mounted\n\n\t\t// reference `messages` array length so that this code re-runs whenever it changes\n\t\tmessages.length;\n\n\t\t// autoscroll when new messages are added\n\t\tif (div.offsetHeight + div.scrollTop > div.scrollHeight - 20) {\n\t\t\ttick().then(() => {\n\t\t\t\tdiv.scrollTo(0, div.scrollHeight);\n\t\t\t});\n\t\t}\n\t});\n</script>\n\n<div bind:this={div}>\n\t{#each messages as message}\n\t\t<p>{message}</p>\n\t{/each}\n</div>\n```\n\nApart from the timing, `$effect.pre` works exactly like `$effect`.\n\n## `$effect.tracking`\n\nThe `$effect.tracking` rune is an advanced feature that tells you whether or not the code is running inside a tracking context, such as an effect or inside your template ([demo](/playground/untitled#H4sIAAAAAAAACn3PwYrCMBDG8VeZDYIt2PYeY8Dn2HrIhqkU08nQjItS-u6buAt7UDzmz8ePyaKGMWBS-nNRcmdU-hHUTpGbyuvI3KZvDFLal0v4qvtIgiSZUSb5eWSxPfWSc4oB2xDP1XYk8HHiSHkICeXKeruDDQ4Demlldv4y0rmq6z10HQwuJMxGVv4mVVXDwcJS0jP9u3knynwtoKz1vifT_Z9Jhm0WBCcOTlDD8kyspmML5qNpHg40jc3fFryJ0iWsp_UHgz3180oBAAA=)):\n\n```svelte\n<script>\n\tconsole.log('in component setup:', $effect.tracking()); // false\n\n\t$effect(() => {\n\t\tconsole.log('in effect:', $effect.tracking()); // true\n\t});\n</script>\n\n<p>in template: {$effect.tracking()}</p> <!-- true -->\n```\n\nIt is used to implement abstractions like [`createSubscriber`](/docs/svelte/svelte-reactivity#createSubscriber), which will create listeners to update reactive values but _only_ if those values are being tracked (rather than, for example, read inside an event handler).\n\n## `$effect.pending`\n\nWhen using [`await`](await-expressions) in components, the `$effect.pending()` rune tells you how many promises are pending in the current [boundary](svelte-boundary), not including child boundaries ([demo](/playground/untitled#H4sIAAAAAAAAE3WRMU_DMBCF_8rJdHDUqilILGkaiY2RgY0yOPYZWbiOFV8IleX_jpMUEAIWS_7u-d27c2ROnJBV7B6t7WDsequAozKEqmAbpo3FwKqnyOjsJ90EMr-8uvN-G97Q0sRaEfAvLjtH6CjbsDrI3nhqju5IFgkEHGAVSBDy62L_SdtvejPTzEU4Owl6cJJM50AoxcUG2gLiVM31URgChyM89N3JBORcF3BoICA9mhN2A3G9gdvdrij2UJYgejLaSCMsKLTivNj0SEOf7WEN7ZwnHV1dfqd2dTsQ5QCdk9bI10PkcxexXqcmH3W51Jt_le2kbH8os9Y3UaTcNLYpDx-Xab6GTHXpZ128MhpWqDVK2np0yrgXXqQpaLa4APDLBkIF8bd2sYql0Sn_DeE7sYr6AdNzvgljR-MUq7SwAdMHeUtgHR4CAAA=)):\n\n```svelte\n<button onclick={() => a++}>a++</button>\n<button onclick={() => b++}>b++</button>\n\n<p>{a} + {b} = {await add(a, b)}</p>\n\n{#if $effect.pending()}\n\t<p>pending promises: {$effect.pending()}</p>\n{/if}\n```\n\n## `$effect.root`\n\nThe `$effect.root` rune is an advanced feature that creates a non-tracked scope that doesn't auto-cleanup. This is useful for nested effects that you want to manually control. This rune also allows for the creation of effects outside of the component initialisation phase.\n\n```js\nconst destroy = $effect.root(() => {\n\t$effect(() => {\n\t\t// setup\n\t});\n\n\treturn () => {\n\t\t// cleanup\n\t};\n});\n\n// later...\ndestroy();\n```\n\n## When not to use `$effect`\n\nIn general, `$effect` is best considered something of an escape hatch — useful for things like analytics and direct DOM manipulation — rather than a tool you should use frequently. In particular, avoid using it to synchronise state. Instead of this...\n\n```svelte\n<script>\n\tlet count = $state(0);\n\tlet doubled = $state();\n\n\t// don't do this!\n\t$effect(() => {\n\t\tdoubled = count * 2;\n\t});\n</script>\n```\n\n...do this:\n\n```svelte\n<script>\n\tlet count = $state(0);\n\tlet doubled = $derived(count * 2);\n</script>\n```\n\n> [!NOTE] For things that are more complicated than a simple expression like `count * 2`, you can also use `$derived.by`.\n\nIf you're using an effect because you want to be able to reassign the derived value (to build an optimistic UI, for example) note that [deriveds can be directly overridden]($derived#Overriding-derived-values) as of Svelte 5.25.\n\nYou might be tempted to do something convoluted with effects to link one value to another. The following example shows two inputs for \"money spent\" and \"money left\" that are connected to each other. If you update one, the other should update accordingly. Don't use effects for this ([demo](/playground/untitled#H4sIAAAAAAAAE5WRTWrDMBCFryKGLBJoY3fRjWIHeoiu6i6UZBwEY0VE49TB-O6VxrFTSih0qe_Ne_OjHpxpEDS8O7ZMeIAnqC1hAP3RA1990hKI_Fb55v06XJA4sZ0J-IjvT47RcYyBIuzP1vO2chVHHFjxiQ2pUr3k-SZRQlbBx_LIFoEN4zJfzQph_UMQr4hRXmBd456Xy5Uqt6pPKHmkfmzyPAZL2PCnbRpg8qWYu63I7lu4gswOSRYqrPNt3CgeqqzgbNwRK1A76w76YqjFspfcQTWmK3vJHlQm1puSTVSeqdOc_r9GaeCHfUSY26TXry6Br4RSK3C6yMEGT-aqVU3YbUZ2NF6rfP2KzXgbuYzY46czdgyazy0On_FlLH3F-UDXhgIO35UGlA1rAgAA)):\n\n```svelte\n<script>\n\tconst total = 100;\n\tlet spent = $state(0);\n\tlet left = $state(total);\n\n\t$effect(() => {\n\t\tleft = total - spent;\n\t});\n\n\t$effect(() => {\n\t\tspent = total - left;\n\t});\n</script>\n\n<label>\n\t<input type=\"range\" bind:value={spent} max={total} />\n\t{spent}/{total} spent\n</label>\n\n<label>\n\t<input type=\"range\" bind:value={left} max={total} />\n\t{left}/{total} left\n</label>\n```\n\nInstead, use `oninput` callbacks or — better still — [function bindings](bind#Function-bindings) where possible ([demo](/playground/untitled#H4sIAAAAAAAAE5VRvW7CMBB-FcvqECQK6dDFJEgsnfoGTQdDLsjSxVjxhYKivHvPBwFUsXS8774_nwftbQva6I_e78gdvNo6Xzu_j3quG4cQtfkaNJ1DIiWA8atkE8IiHgEpYVsb4Rm-O3gCT2yji7jrXKB15StiOJKiA1lUpXrL81VCEUjFwHTGXiJZgiyf3TYIjSxq6NwR6uyifr0ohMbEZnpHH2rWf7ImS8KZGtK6osl_UqelRIyVL5b3ir5AuwWUtoXzoee6fIWy0p31e6i0XMocLfZQDuI6qtaeykGcR7UU6XWznFAZU9LN_X9B2UyVayk9f3ji0-REugen6U9upDOCcAWcLlS7GNCejWoQTqsLtrfBqHzxDu3DrUTOf0xwIm2o62H85sk6_OHG2jQWI4y_3byXXGMCAAA=)):\n\n```svelte\n<script>\n\tconst total = 100;\n\tlet spent = $state(0);\n\tlet left = $derived(total - spent);\n\n+++\tfunction updateLeft(left) {\n\t\tspent = total - left;\n\t}+++\n</script>\n\n<label>\n\t<input type=\"range\" bind:value={spent} max={total} />\n\t{spent}/{total} spent\n</label>\n\n<label>\n\t<input type=\"range\" +++bind:value={() => left, updateLeft}+++ max={total} />\n\t{left}/{total} left\n</label>\n```\n\nIf you absolutely have to update `$state` within an effect and run into an infinite loop because you read and write to the same `$state`, use [untrack](svelte#untrack)."
}
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{
"code": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>",
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"text": "{\"issues\":[],\"suggestions\":[\"You are calling a function inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use `$derived` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.\",\"You are calling a function inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use `$derived` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.\",\"Do not use $inspect directive at line 6, column 3\",\"Do not use $inspect directive at line 9, column 3\",\"Do not use $inspect directive at line 17, column 5\"],\"require_another_tool_call_after_fixing\":true}"
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"issues": [],
"suggestions": [
"You are calling a function inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use `$derived` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.",
"You are calling a function inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use `$derived` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.",
"Do not use $inspect directive at line 6, column 3",
"Do not use $inspect directive at line 9, column 3",
"Do not use $inspect directive at line 17, column 5"
],
"require_another_tool_call_after_fixing": true
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{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 1162,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
}
]
}
{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 1036,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
}
]
}
{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 1056,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
}
]
}
{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes - call this at the top level\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 883,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
}
]
}
{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 1001,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
}
]
}
{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes - will log init on mount\n $inspect(text);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 956,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\nEffect triggered - updat…' to contain 'init'"
}
]
}
{
"content": "<script>\n let text = $state('Hello world');\n let charCount = $derived(text.length);\n\n // Basic $inspect to log state changes - will log init on mount\n $inspect(text);\n $inspect(charCount);\n\n // $inspect.with to track updates with custom callback\n $inspect(charCount).with((type, count) => {\n if (type === 'update') {\n console.log(`Character count updated: ${count}`);\n }\n });\n\n // $inspect.trace inside an effect\n $effect(() => {\n $inspect.trace();\n console.log('Effect triggered - updating character count display');\n });\n</script>\n\n<div>\n <h2>Inspect Demo</h2>\n \n <label for=\"text-input\">\n Enter text:\n <input\n id=\"text-input\"\n type=\"text\"\n bind:value={text}\n data-testid=\"text-input\"\n />\n </label>\n\n <div data-testid=\"text-value\">\n Current text: \"{text}\"\n </div>\n\n <div data-testid=\"char-count\">\n Character count: {charCount}\n </div>\n</div>"
}
{
"success": false,
"message": "3 of 4 tests failed",
"passed": 1,
"failed": 3,
"total": 4,
"duration": 902,
"validationFailed": false,
"validation": {
"valid": true,
"errors": []
},
"error": "expected 'Hello world\\n11\\nEffect triggered - u…' to contain 'init'",
"failedTests": [
{
"name": "InspectDemo component > updates text value and character count when input changes",
"error": "expected 'Hello world\\n11\\nEffect triggered - u…' to contain 'init'"
},
{
"name": "InspectDemo component > handles special characters correctly",
"error": "expected 'Hello world\\n11\\nEffect triggered - u…' to contain 'init'"
},
{
"name": "InspectDemo component > handles empty input correctly",
"error": "expected 'Hello world\\n11\\nEffect triggered - u…' to contain 'init'"
}
]
}
Create a Svelte 5 component that uses the `$props` rune to accept component properties.
The component should accept props for `name` (default "World"), `count` (default 0), and `showDetails` (default false). Display the name in a heading, show the count with an increment button, and conditionally display details when `showDetails` is true.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import userEvent from "@testing-library/user-event";
import PropsDemo from "./Component.svelte"; // Path to the generated component
describe("PropsDemo component", () => {
test("renders with default props", () => {
render(PropsDemo);
// Check default values
const nameDisplay = screen.getByTestId("name-display");
const countDisplay = screen.getByTestId("count-display");
expect(nameDisplay).toHaveTextContent("World");
// Just check for the number 0 without requiring "Count: " prefix
expect(countDisplay.textContent).toMatch(/0/);
// Details should not be visible by default
expect(screen.queryByTestId("details")).not.toBeInTheDocument();
});
test("renders with custom props", () => {
render(PropsDemo, {
props: { name: "Svelte", count: 5, showDetails: true },
});
// Check custom values
const nameDisplay = screen.getByTestId("name-display");
const countDisplay = screen.getByTestId("count-display");
const details = screen.getByTestId("details");
expect(nameDisplay).toHaveTextContent("Svelte");
// Just check for the number 5 without requiring specific text before it
expect(countDisplay.textContent).toMatch(/5/);
expect(details).toBeInTheDocument();
// Check for values without requiring specific text format
expect(details.textContent).toMatch(/Svelte/);
expect(details.textContent).toMatch(/5/);
expect(details.textContent).toMatch(/true/i); // case insensitive match for "true"
});
test("increment button increases count", async () => {
const user = userEvent.setup();
render(PropsDemo, { props: { count: 10 } });
const incrementButton = screen.getByTestId("increment-button");
const countDisplay = screen.getByTestId("count-display");
// Initial count should be 10, without requiring "Count: " prefix
expect(countDisplay.textContent).toMatch(/10/);
// Click the increment button
await user.click(incrementButton);
// Count should now be 11, without requiring "Count: " prefix
expect(countDisplay.textContent).toMatch(/11/);
});
test("conditional rendering works correctly", () => {
// First render without details
const { unmount } = render(PropsDemo, { props: { showDetails: false } });
expect(screen.queryByTestId("details")).not.toBeInTheDocument();
// Unmount and render again with details
unmount();
render(PropsDemo, { props: { showDetails: true } });
expect(screen.getByTestId("details")).toBeInTheDocument();
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{}
{
"content": [
{
"type": "text",
"text": "List of available Svelte documentation sections with their intended use cases. The \"use_cases\" field describes WHEN each section would be useful - analyze these carefully to determine which sections match the user's query:\n\n- title: Overview, use_cases: project setup, creating new svelte apps, scaffolding, cli tools, initializing projects, path: cli/overview\n- title: Frequently asked questions, use_cases: project setup, initializing new svelte projects, troubleshooting cli installation, package manager configuration, path: cli/faq\n- title: sv create, use_cases: project setup, starting new sveltekit app, initializing project, creating from playground, choosing project template, path: cli/sv-create\n- title: sv add, use_cases: project setup, adding features to existing projects, integrating tools, testing setup, styling setup, authentication, database setup, deployment adapters, path: cli/sv-add\n- title: sv check, use_cases: code quality, ci/cd pipelines, error checking, typescript projects, pre-commit hooks, finding unused css, accessibility auditing, production builds, path: cli/sv-check\n- title: sv migrate, use_cases: migration, upgrading svelte versions, upgrading sveltekit versions, modernizing codebase, svelte 3 to 4, svelte 4 to 5, sveltekit 1 to 2, adopting runes, refactoring deprecated apis, path: cli/sv-migrate\n- title: devtools-json, use_cases: development setup, chrome devtools integration, browser-based editing, local development workflow, debugging setup, path: cli/devtools-json\n- title: drizzle, use_cases: database setup, sql queries, orm integration, data modeling, postgresql, mysql, sqlite, server-side data access, database migrations, type-safe queries, path: cli/drizzle\n- title: eslint, use_cases: code quality, linting, error detection, project setup, code standards, team collaboration, typescript projects, path: cli/eslint\n- title: lucia, use_cases: authentication, login systems, user management, registration pages, session handling, auth setup, path: cli/lucia\n- title: mcp, use_cases: use title and path to estimate use case, path: cli/mcp\n- title: mdsvex, use_cases: blog, content sites, markdown rendering, documentation sites, technical writing, cms integration, article pages, path: cli/mdsvex\n- title: paraglide, use_cases: internationalization, multi-language sites, i18n, translation, localization, language switching, global apps, multilingual content, path: cli/paraglide\n- title: playwright, use_cases: browser testing, e2e testing, integration testing, test automation, quality assurance, ci/cd pipelines, testing user flows, path: cli/playwright\n- title: prettier, use_cases: code formatting, project setup, code style consistency, team collaboration, linting configuration, path: cli/prettier\n- title: storybook, use_cases: component development, design systems, ui library, isolated component testing, documentation, visual testing, component showcase, path: cli/storybook\n- title: sveltekit-adapter, use_cases: deployment, production builds, hosting setup, choosing deployment platform, configuring adapters, static site generation, node server, vercel, cloudflare, netlify, path: cli/sveltekit-adapter\n- title: tailwindcss, use_cases: project setup, styling, css framework, rapid prototyping, utility-first css, design systems, responsive design, adding tailwind to svelte, path: cli/tailwind\n- title: vitest, use_cases: testing, unit tests, component testing, test setup, quality assurance, ci/cd pipelines, test-driven development, path: cli/vitest\n- title: Introduction, use_cases: learning sveltekit, project setup, understanding framework basics, choosing between svelte and sveltekit, getting started with full-stack apps, path: kit/introduction\n- title: Creating a project, use_cases: project setup, starting new sveltekit app, initial development environment, first-time sveltekit users, scaffolding projects, path: kit/creating-a-project\n- title: Project types, use_cases: deployment, project setup, choosing adapters, ssg, spa, ssr, serverless, mobile apps, desktop apps, pwa, offline apps, browser extensions, separate backend, docker containers, path: kit/project-types\n- title: Project structure, use_cases: project setup, understanding file structure, organizing code, starting new project, learning sveltekit basics, path: kit/project-structure\n- title: Web standards, use_cases: always, any sveltekit project, data fetching, forms, api routes, server-side rendering, deployment to various platforms, path: kit/web-standards\n- title: Routing, use_cases: routing, navigation, multi-page apps, project setup, file structure, api endpoints, data loading, layouts, error pages, always, path: kit/routing\n- title: Loading data, use_cases: data fetching, api calls, database queries, dynamic routes, page initialization, loading states, authentication checks, ssr data, form data, content rendering, path: kit/load\n- title: Form actions, use_cases: forms, user input, data submission, authentication, login systems, user registration, progressive enhancement, validation errors, path: kit/form-actions\n- title: Page options, use_cases: prerendering static sites, ssr configuration, spa setup, client-side rendering control, url trailing slash handling, adapter deployment config, build optimization, path: kit/page-options\n- title: State management, use_cases: sveltekit, server-side rendering, ssr, state management, authentication, data persistence, load functions, context api, navigation, component lifecycle, path: kit/state-management\n- title: Remote functions, use_cases: data fetching, server-side logic, database queries, type-safe client-server communication, forms, user input, mutations, authentication, crud operations, optimistic updates, path: kit/remote-functions\n- title: Building your app, use_cases: production builds, deployment preparation, build process optimization, adapter configuration, preview before deployment, path: kit/building-your-app\n- title: Adapters, use_cases: deployment, production builds, hosting setup, choosing deployment platform, configuring adapters, path: kit/adapters\n- title: Zero-config deployments, use_cases: deployment, production builds, hosting setup, choosing deployment platform, ci/cd configuration, path: kit/adapter-auto\n- title: Node servers, use_cases: deployment, production builds, node.js hosting, custom server setup, environment configuration, reverse proxy setup, docker deployment, systemd services, path: kit/adapter-node\n- title: Static site generation, use_cases: static site generation, ssg, prerendering, deployment, github pages, spa mode, blogs, documentation sites, marketing sites, path: kit/adapter-static\n- title: Single-page apps, use_cases: spa mode, single-page apps, client-only rendering, static hosting, mobile app wrappers, no server-side logic, adapter-static setup, fallback pages, path: kit/single-page-apps\n- title: Cloudflare, use_cases: deployment, cloudflare workers, cloudflare pages, hosting setup, production builds, serverless deployment, edge computing, path: kit/adapter-cloudflare\n- title: Cloudflare Workers, use_cases: deploying to cloudflare workers, cloudflare workers sites deployment, legacy cloudflare adapter, wrangler configuration, cloudflare platform bindings, path: kit/adapter-cloudflare-workers\n- title: Netlify, use_cases: deployment, netlify hosting, production builds, serverless functions, edge functions, static site hosting, path: kit/adapter-netlify\n- title: Vercel, use_cases: deployment, vercel hosting, production builds, serverless functions, edge functions, isr, image optimization, environment variables, path: kit/adapter-vercel\n- title: Writing adapters, use_cases: custom deployment, building adapters, unsupported platforms, adapter development, custom hosting environments, path: kit/writing-adapters\n- title: Advanced routing, use_cases: advanced routing, dynamic routes, file viewers, nested paths, custom 404 pages, url validation, route parameters, multi-level navigation, path: kit/advanced-routing\n- title: Hooks, use_cases: authentication, logging, error tracking, request interception, api proxying, custom routing, internationalization, database initialization, middleware logic, session management, path: kit/hooks\n- title: Errors, use_cases: error handling, custom error pages, 404 pages, api error responses, production error logging, error tracking, type-safe errors, path: kit/errors\n- title: Link options, use_cases: routing, navigation, multi-page apps, performance optimization, link preloading, forms with get method, search functionality, focus management, scroll behavior, path: kit/link-options\n- title: Service workers, use_cases: offline support, pwa, caching strategies, performance optimization, precaching assets, network resilience, progressive web apps, path: kit/service-workers\n- title: Server-only modules, use_cases: api keys, environment variables, sensitive data protection, backend security, preventing data leaks, server-side code isolation, path: kit/server-only-modules\n- title: Snapshots, use_cases: forms, user input, preserving form data, multi-step forms, navigation state, preventing data loss, textarea content, input fields, comment systems, surveys, path: kit/snapshots\n- title: Shallow routing, use_cases: modals, dialogs, image galleries, overlays, history-driven ui, mobile-friendly navigation, photo viewers, lightboxes, drawer menus, path: kit/shallow-routing\n- title: Observability, use_cases: performance monitoring, debugging, observability, tracing requests, production diagnostics, analyzing slow requests, finding bottlenecks, monitoring server-side operations, path: kit/observability\n- title: Packaging, use_cases: building component libraries, publishing npm packages, creating reusable svelte components, library development, package distribution, path: kit/packaging\n- title: Auth, use_cases: authentication, login systems, user management, session handling, jwt tokens, protected routes, user credentials, authorization checks, path: kit/auth\n- title: Performance, use_cases: performance optimization, slow loading pages, production deployment, debugging performance issues, reducing bundle size, improving load times, path: kit/performance\n- title: Icons, use_cases: icons, ui components, styling, css frameworks, tailwind, unocss, performance optimization, dependency management, path: kit/icons\n- title: Images, use_cases: image optimization, responsive images, performance, hero images, product photos, galleries, cms integration, cdn setup, asset management, path: kit/images\n- title: Accessibility, use_cases: always, any sveltekit project, screen reader support, keyboard navigation, multi-page apps, client-side routing, internationalization, multilingual sites, path: kit/accessibility\n- title: SEO, use_cases: seo optimization, search engine ranking, content sites, blogs, marketing sites, public-facing apps, sitemaps, amp pages, meta tags, performance optimization, path: kit/seo\n- title: Frequently asked questions, use_cases: troubleshooting package imports, library compatibility issues, client-side code execution, external api integration, middleware setup, database configuration, view transitions, yarn configuration, path: kit/faq\n- title: Integrations, use_cases: project setup, css preprocessors, postcss, scss, sass, less, stylus, typescript setup, adding integrations, tailwind, testing, auth, linting, formatting, path: kit/integrations\n- title: Breakpoint Debugging, use_cases: debugging, breakpoints, development workflow, troubleshooting issues, vscode setup, ide configuration, inspecting code execution, path: kit/debugging\n- title: Migrating to SvelteKit v2, use_cases: migration, upgrading from sveltekit 1 to 2, breaking changes, version updates, path: kit/migrating-to-sveltekit-2\n- title: Migrating from Sapper, use_cases: migrating from sapper, upgrading legacy projects, sapper to sveltekit conversion, project modernization, path: kit/migrating\n- title: Additional resources, use_cases: troubleshooting, getting help, finding examples, learning sveltekit, project templates, common issues, community support, path: kit/additional-resources\n- title: Glossary, use_cases: rendering strategies, performance optimization, deployment configuration, seo requirements, static sites, spas, server-side rendering, prerendering, edge deployment, pwa development, path: kit/glossary\n- title: @sveltejs/kit, use_cases: forms, form actions, server-side validation, form submission, error handling, redirects, json responses, http errors, server utilities, path: kit/@sveltejs-kit\n- title: @sveltejs/kit/hooks, use_cases: middleware, request processing, authentication chains, logging, multiple hooks, request/response transformation, path: kit/@sveltejs-kit-hooks\n- title: @sveltejs/kit/node/polyfills, use_cases: node.js environments, custom servers, non-standard runtimes, ssr setup, web api compatibility, polyfill requirements, path: kit/@sveltejs-kit-node-polyfills\n- title: @sveltejs/kit/node, use_cases: node.js adapter, custom server setup, http integration, streaming files, node deployment, server-side rendering with node, path: kit/@sveltejs-kit-node\n- title: @sveltejs/kit/vite, use_cases: project setup, vite configuration, initial sveltekit setup, build tooling, path: kit/@sveltejs-kit-vite\n- title: $app/environment, use_cases: always, conditional logic, client-side code, server-side code, build-time logic, prerendering, development vs production, environment detection, path: kit/$app-environment\n- title: $app/forms, use_cases: forms, user input, data submission, progressive enhancement, custom form handling, form validation, path: kit/$app-forms\n- title: $app/navigation, use_cases: routing, navigation, multi-page apps, programmatic navigation, data reloading, preloading, shallow routing, navigation lifecycle, scroll handling, view transitions, path: kit/$app-navigation\n- title: $app/paths, use_cases: static assets, images, fonts, public files, base path configuration, subdirectory deployment, cdn setup, asset urls, links, navigation, path: kit/$app-paths\n- title: $app/server, use_cases: remote functions, server-side logic, data fetching, form handling, api endpoints, client-server communication, prerendering, file reading, batch queries, path: kit/$app-server\n- title: $app/state, use_cases: routing, navigation, multi-page apps, loading states, url parameters, form handling, error states, version updates, page metadata, shallow routing, path: kit/$app-state\n- title: $app/stores, use_cases: legacy projects, sveltekit pre-2.12, migration from stores to runes, maintaining older codebases, accessing page data, navigation state, app version updates, path: kit/$app-stores\n- title: $app/types, use_cases: routing, navigation, type safety, route parameters, dynamic routes, link generation, pathname validation, multi-page apps, path: kit/$app-types\n- title: $env/dynamic/private, use_cases: api keys, secrets management, server-side config, environment variables, backend logic, deployment-specific settings, private data handling, path: kit/$env-dynamic-private\n- title: $env/dynamic/public, use_cases: environment variables, client-side config, runtime configuration, public api keys, deployment-specific settings, multi-environment apps, path: kit/$env-dynamic-public\n- title: $env/static/private, use_cases: server-side api keys, backend secrets, database credentials, private configuration, build-time optimization, server endpoints, authentication tokens, path: kit/$env-static-private\n- title: $env/static/public, use_cases: environment variables, public config, client-side data, api endpoints, build-time configuration, public constants, path: kit/$env-static-public\n- title: $lib, use_cases: project setup, component organization, importing shared components, reusable ui elements, code structure, path: kit/$lib\n- title: $service-worker, use_cases: offline support, pwa, service workers, caching strategies, progressive web apps, offline-first apps, path: kit/$service-worker\n- title: Configuration, use_cases: project setup, configuration, adapters, deployment, build settings, environment variables, routing customization, prerendering, csp security, csrf protection, path configuration, typescript setup, path: kit/configuration\n- title: Command Line Interface, use_cases: project setup, typescript configuration, generated types, ./$types imports, initial project configuration, path: kit/cli\n- title: Types, use_cases: typescript, type safety, route parameters, api endpoints, load functions, form actions, generated types, jsconfig setup, path: kit/types\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/overview\n- title: Local setup, use_cases: use title and path to estimate use case, path: mcp/local-setup\n- title: Remote setup, use_cases: use title and path to estimate use case, path: mcp/remote-setup\n- title: Tools, use_cases: use title and path to estimate use case, path: mcp/tools\n- title: Resources, use_cases: use title and path to estimate use case, path: mcp/resources\n- title: Prompts, use_cases: use title and path to estimate use case, path: mcp/prompts\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/plugin\n- title: Skill, use_cases: use title and path to estimate use case, path: mcp/skill\n- title: Subagent, use_cases: use title and path to estimate use case, path: mcp/subagent\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/opencode-plugin\n- title: Subagent, use_cases: use title and path to estimate use case, path: mcp/opencode-subagent\n- title: Overview, use_cases: always, any svelte project, getting started, learning svelte, introduction, project setup, understanding framework basics, path: svelte/overview\n- title: Getting started, use_cases: project setup, starting new svelte project, initial installation, choosing between sveltekit and vite, editor configuration, path: svelte/getting-started\n- title: .svelte files, use_cases: always, any svelte project, component creation, project setup, learning svelte basics, path: svelte/svelte-files\n- title: .svelte.js and .svelte.ts files, use_cases: shared reactive state, reusable reactive logic, state management across components, global stores, custom reactive utilities, path: svelte/svelte-js-files\n- title: What are runes?, use_cases: always, any svelte 5 project, understanding core syntax, learning svelte 5, migration from svelte 4, path: svelte/what-are-runes\n- title: $state, use_cases: always, any svelte project, core reactivity, state management, counters, forms, todo apps, interactive ui, data updates, class-based components, path: svelte/$state\n- title: $derived, use_cases: always, any svelte project, computed values, reactive calculations, derived data, transforming state, dependent values, path: svelte/$derived\n- title: $effect, use_cases: canvas drawing, third-party library integration, dom manipulation, side effects, intervals, timers, network requests, analytics tracking, path: svelte/$effect\n- title: $props, use_cases: always, any svelte project, passing data to components, component communication, reusable components, component props, path: svelte/$props\n- title: $bindable, use_cases: forms, user input, two-way data binding, custom input components, parent-child communication, reusable form fields, path: svelte/$bindable\n- title: $inspect, use_cases: debugging, development, tracking state changes, reactive state monitoring, troubleshooting reactivity issues, path: svelte/$inspect\n- title: $host, use_cases: custom elements, web components, dispatching custom events, component library, framework-agnostic components, path: svelte/$host\n- title: Basic markup, use_cases: always, any svelte project, basic markup, html templating, component structure, attributes, events, props, text rendering, path: svelte/basic-markup\n- title: {#if ...}, use_cases: always, conditional rendering, showing/hiding content, dynamic ui, user permissions, loading states, error handling, form validation, path: svelte/if\n- title: {#each ...}, use_cases: always, lists, arrays, iteration, product listings, todos, tables, grids, dynamic content, shopping carts, user lists, comments, feeds, path: svelte/each\n- title: {#key ...}, use_cases: animations, transitions, component reinitialization, forcing component remount, value-based ui updates, resetting component state, path: svelte/key\n- title: {#await ...}, use_cases: async data fetching, api calls, loading states, promises, error handling, lazy loading components, dynamic imports, path: svelte/await\n- title: {#snippet ...}, use_cases: reusable markup, component composition, passing content to components, table rows, list items, conditional rendering, reducing duplication, path: svelte/snippet\n- title: {@render ...}, use_cases: reusable ui patterns, component composition, conditional rendering, fallback content, layout components, slot alternatives, template reuse, path: svelte/@render\n- title: {@html ...}, use_cases: rendering html strings, cms content, rich text editors, markdown to html, blog posts, wysiwyg output, sanitized html injection, dynamic html content, path: svelte/@html\n- title: {@attach ...}, use_cases: tooltips, popovers, dom manipulation, third-party libraries, canvas drawing, element lifecycle, interactive ui, custom directives, wrapper components, path: svelte/@attach\n- title: {@const ...}, use_cases: computed values in loops, derived calculations in blocks, local variables in each iterations, complex list rendering, path: svelte/@const\n- title: {@debug ...}, use_cases: debugging, development, troubleshooting, tracking state changes, monitoring variables, reactive data inspection, path: svelte/@debug\n- title: bind:, use_cases: forms, user input, two-way data binding, interactive ui, media players, file uploads, checkboxes, radio buttons, select dropdowns, contenteditable, dimension tracking, path: svelte/bind\n- title: use:, use_cases: custom directives, dom manipulation, third-party library integration, tooltips, click outside, gestures, focus management, element lifecycle hooks, path: svelte/use\n- title: transition:, use_cases: animations, interactive ui, modals, dropdowns, notifications, conditional content, show/hide elements, smooth state changes, path: svelte/transition\n- title: in: and out:, use_cases: animation, transitions, interactive ui, conditional rendering, independent enter/exit effects, modals, tooltips, notifications, path: svelte/in-and-out\n- title: animate:, use_cases: sortable lists, drag and drop, reorderable items, todo lists, kanban boards, playlist editors, priority queues, animated list reordering, path: svelte/animate\n- title: style:, use_cases: dynamic styling, conditional styles, theming, dark mode, responsive design, interactive ui, component styling, path: svelte/style\n- title: class, use_cases: always, conditional styling, dynamic classes, tailwind css, component styling, reusable components, responsive design, path: svelte/class\n- title: await, use_cases: async data fetching, loading states, server-side rendering, awaiting promises in components, async validation, concurrent data loading, path: svelte/await-expressions\n- title: Scoped styles, use_cases: always, styling components, scoped css, component-specific styles, preventing style conflicts, animations, keyframes, path: svelte/scoped-styles\n- title: Global styles, use_cases: global styles, third-party libraries, css resets, animations, styling body/html, overriding component styles, shared keyframes, base styles, path: svelte/global-styles\n- title: Custom properties, use_cases: theming, custom styling, reusable components, design systems, dynamic colors, component libraries, ui customization, path: svelte/custom-properties\n- title: Nested <style> elements, use_cases: component styling, scoped styles, dynamic styles, conditional styling, nested style tags, custom styling logic, path: svelte/nested-style-elements\n- title: <svelte:boundary>, use_cases: error handling, async data loading, loading states, error recovery, flaky components, error reporting, resilient ui, path: svelte/svelte-boundary\n- title: <svelte:window>, use_cases: keyboard shortcuts, scroll tracking, window resize handling, responsive layouts, online/offline detection, viewport dimensions, global event listeners, path: svelte/svelte-window\n- title: <svelte:document>, use_cases: document events, visibility tracking, fullscreen detection, pointer lock, focus management, document-level interactions, path: svelte/svelte-document\n- title: <svelte:body>, use_cases: mouse tracking, hover effects, cursor interactions, global body events, drag and drop, custom cursors, interactive backgrounds, body-level actions, path: svelte/svelte-body\n- title: <svelte:head>, use_cases: seo optimization, page titles, meta tags, social media sharing, dynamic head content, multi-page apps, blog posts, product pages, path: svelte/svelte-head\n- title: <svelte:element>, use_cases: dynamic content, cms integration, user-generated content, configurable ui, runtime element selection, flexible components, path: svelte/svelte-element\n- title: <svelte:options>, use_cases: migration, custom elements, web components, legacy mode compatibility, runes mode setup, svg components, mathml components, css injection control, path: svelte/svelte-options\n- title: Stores, use_cases: shared state, cross-component data, reactive values, async data streams, manual control over updates, rxjs integration, extracting logic, path: svelte/stores\n- title: Context, use_cases: shared state, avoiding prop drilling, component communication, theme providers, user context, authentication state, configuration sharing, deeply nested components, path: svelte/context\n- title: Lifecycle hooks, use_cases: component initialization, cleanup tasks, timers, subscriptions, dom measurements, chat windows, autoscroll features, migration from svelte 4, path: svelte/lifecycle-hooks\n- title: Imperative component API, use_cases: project setup, client-side rendering, server-side rendering, ssr, hydration, testing, programmatic component creation, tooltips, dynamic mounting, path: svelte/imperative-component-api\n- title: Hydratable data, use_cases: use title and path to estimate use case, path: svelte/hydratable\n- title: Testing, use_cases: testing, quality assurance, unit tests, integration tests, component tests, e2e tests, vitest setup, playwright setup, test automation, path: svelte/testing\n- title: TypeScript, use_cases: typescript setup, type safety, component props typing, generic components, wrapper components, dom type augmentation, project configuration, path: svelte/typescript\n- title: Custom elements, use_cases: web components, custom elements, component library, design system, framework-agnostic components, embedding svelte in non-svelte apps, shadow dom, path: svelte/custom-elements\n- title: Svelte 4 migration guide, use_cases: upgrading svelte 3 to 4, version migration, updating dependencies, breaking changes, legacy project maintenance, path: svelte/v4-migration-guide\n- title: Svelte 5 migration guide, use_cases: migrating from svelte 4 to 5, upgrading projects, learning svelte 5 syntax changes, runes migration, event handler updates, path: svelte/v5-migration-guide\n- title: Frequently asked questions, use_cases: getting started, learning svelte, beginner setup, project initialization, vs code setup, formatting, testing, routing, mobile apps, troubleshooting, community support, path: svelte/faq\n- title: svelte, use_cases: migration from svelte 4 to 5, upgrading legacy code, component lifecycle hooks, context api, mounting components, event dispatchers, typescript component types, path: svelte/svelte\n- title: svelte/action, use_cases: typescript types, actions, use directive, dom manipulation, element lifecycle, custom behaviors, third-party library integration, path: svelte/svelte-action\n- title: svelte/animate, use_cases: animated lists, sortable items, drag and drop, reordering elements, todo lists, kanban boards, playlist management, smooth position transitions, path: svelte/svelte-animate\n- title: svelte/attachments, use_cases: library development, component libraries, programmatic element manipulation, migrating from actions to attachments, spreading props onto elements, path: svelte/svelte-attachments\n- title: svelte/compiler, use_cases: build tools, custom compilers, ast manipulation, preprocessors, code transformation, migration scripts, syntax analysis, bundler plugins, dev tools, path: svelte/svelte-compiler\n- title: svelte/easing, use_cases: animations, transitions, custom easing, smooth motion, interactive ui, modals, dropdowns, carousels, page transitions, scroll effects, path: svelte/svelte-easing\n- title: svelte/events, use_cases: window events, document events, global event listeners, event delegation, programmatic event handling, cleanup functions, media queries, path: svelte/svelte-events\n- title: svelte/legacy, use_cases: migration from svelte 4 to svelte 5, upgrading legacy code, event modifiers, class components, imperative component instantiation, path: svelte/svelte-legacy\n- title: svelte/motion, use_cases: animation, smooth transitions, interactive ui, sliders, counters, physics-based motion, drag gestures, accessibility, reduced motion, path: svelte/svelte-motion\n- title: svelte/reactivity/window, use_cases: responsive design, viewport tracking, scroll effects, window resize handling, online/offline detection, zoom level tracking, path: svelte/svelte-reactivity-window\n- title: svelte/reactivity, use_cases: reactive data structures, state management with maps/sets, game boards, selection tracking, url manipulation, query params, real-time clocks, media queries, responsive design, path: svelte/svelte-reactivity\n- title: svelte/server, use_cases: server-side rendering, ssr, static site generation, seo optimization, initial page load, pre-rendering, node.js server, custom server setup, path: svelte/svelte-server\n- title: svelte/store, use_cases: state management, shared data, reactive stores, cross-component communication, global state, computed values, data synchronization, legacy svelte projects, path: svelte/svelte-store\n- title: svelte/transition, use_cases: animations, transitions, interactive ui, modals, dropdowns, tooltips, notifications, svg animations, list animations, page transitions, path: svelte/svelte-transition\n- title: Compiler errors, use_cases: animation, transitions, keyed each blocks, list animations, path: svelte/compiler-errors\n- title: Compiler warnings, use_cases: accessibility, a11y compliance, wcag standards, screen readers, keyboard navigation, aria attributes, semantic html, interactive elements, path: svelte/compiler-warnings\n- title: Runtime errors, use_cases: debugging errors, error handling, troubleshooting runtime issues, migration to svelte 5, component binding, effects and reactivity, path: svelte/runtime-errors\n- title: Runtime warnings, use_cases: debugging state proxies, console logging reactive values, inspecting state changes, development troubleshooting, path: svelte/runtime-warnings\n- title: Overview, use_cases: migrating from svelte 3/4 to svelte 5, maintaining legacy components, understanding deprecated features, gradual upgrade process, path: svelte/legacy-overview\n- title: Reactive let/var declarations, use_cases: migration, legacy svelte projects, upgrading from svelte 4, understanding old reactivity, maintaining existing code, learning runes differences, path: svelte/legacy-let\n- title: Reactive $: statements, use_cases: legacy mode, migration from svelte 4, reactive statements, computed values, derived state, side effects, path: svelte/legacy-reactive-assignments\n- title: export let, use_cases: legacy mode, migration from svelte 4, maintaining older projects, component props without runes, exporting component methods, renaming reserved word props, path: svelte/legacy-export-let\n- title: $$props and $$restProps, use_cases: legacy mode migration, component wrappers, prop forwarding, button components, reusable ui components, spreading props to child elements, path: svelte/legacy-$$props-and-$$restProps\n- title: on:, use_cases: legacy mode, event handling, button clicks, forms, user interactions, component communication, event forwarding, event modifiers, path: svelte/legacy-on\n- title: <slot>, use_cases: legacy mode, migrating from svelte 4, component composition, reusable components, passing content to components, modals, layouts, wrappers, path: svelte/legacy-slots\n- title: $$slots, use_cases: legacy mode, conditional slot rendering, optional content sections, checking if slots provided, migrating from legacy to runes, path: svelte/legacy-$$slots\n- title: <svelte:fragment>, use_cases: named slots, component composition, layout systems, avoiding wrapper divs, legacy svelte projects, slot content organization, path: svelte/legacy-svelte-fragment\n- title: <svelte:component>, use_cases: dynamic components, component switching, conditional rendering, legacy mode migration, tabbed interfaces, multi-step forms, path: svelte/legacy-svelte-component\n- title: <svelte:self>, use_cases: recursive components, tree structures, nested menus, file explorers, comment threads, hierarchical data, path: svelte/legacy-svelte-self\n- title: Imperative component API, use_cases: migration from svelte 3/4 to 5, legacy component api, maintaining old projects, understanding deprecated patterns, path: svelte/legacy-component-api\n\nCarefully analyze the use_cases field for each section to identify which documentation is relevant for the user's specific query. The use_cases contain keywords for project types, features, components, and development stages. After identifying relevant sections, use the get-documentation tool with ALL relevant section titles or paths at once (can pass multiple sections as an array)."
}
],
"isError": false
}
{
"section": "[\"$props\", \"{#if ...}\", \"Basic markup\"]"
}
{
"content": [
{
"type": "text",
"text": "## $props\n\nThe inputs to a component are referred to as _props_, which is short for _properties_. You pass props to components just like you pass attributes to elements:\n\n```svelte\n<!--- file: App.svelte --->\n<script>\n\timport MyComponent from './MyComponent.svelte';\n</script>\n\n<MyComponent adjective=\"cool\" />\n```\n\nOn the other side, inside `MyComponent.svelte`, we can receive props with the `$props` rune...\n\n```svelte\n<!--- file: MyComponent.svelte --->\n<script>\n\tlet props = $props();\n</script>\n\n<p>this component is {props.adjective}</p>\n```\n\n...though more commonly, you'll [_destructure_](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment) your props:\n\n```svelte\n<!--- file: MyComponent.svelte --->\n<script>\n\tlet +++{ adjective }+++ = $props();\n</script>\n\n<p>this component is {+++adjective+++}</p>\n```\n\n## Fallback values\n\nDestructuring allows us to declare fallback values, which are used if the parent component does not set a given prop (or the value is `undefined`):\n\n```js\nlet { adjective = 'happy' } = $props();\n```\n\n> [!NOTE] Fallback values are not turned into reactive state proxies (see [Updating props](#Updating-props) for more info)\n\n## Renaming props\n\nWe can also use the destructuring assignment to rename props, which is necessary if they're invalid identifiers, or a JavaScript keyword like `super`:\n\n```js\nlet { super: trouper = 'lights are gonna find me' } = $props();\n```\n\n## Rest props\n\nFinally, we can use a _rest property_ to get, well, the rest of the props:\n\n```js\nlet { a, b, c, ...others } = $props();\n```\n\n## Updating props\n\nReferences to a prop inside a component update when the prop itself updates — when `count` changes in `App.svelte`, it will also change inside `Child.svelte`. But the child component is able to temporarily override the prop value, which can be useful for unsaved ephemeral state ([demo](/playground/untitled#H4sIAAAAAAAAE6WQ0WrDMAxFf0WIQR0Wmu3VTQJln7HsIfVcZubIxlbGRvC_DzuBraN92qPula50tODZWB1RPi_IX16jLALWSOOUq6P3-_ihLWftNEZ9TVeOWBNHlNhGFYznfqCBzeRdYHh6M_YVzsFNsNs3pdpGd4eBcqPVDMrNxNDBXeSRtXioDgO1zU8ataeZ2RE4Utao924RFXQ9iHXwvoPHKpW1xY4g_Bg0cSVhKS0p560Za95612ZC02ONrD8ZJYdZp_rGQ37ff_mSP86Np2TWZaNNmdcH56P4P67K66_SXoK9pG-5dF5Z9QEAAA==)):\n\n```svelte\n<!--- file: App.svelte --->\n<script>\n\timport Child from './Child.svelte';\n\n\tlet count = $state(0);\n</script>\n\n<button onclick={() => (count += 1)}>\n\tclicks (parent): {count}\n</button>\n\n<Child {count} />\n```\n\n```svelte\n<!--- file: Child.svelte --->\n<script>\n\tlet { count } = $props();\n</script>\n\n<button onclick={() => (count += 1)}>\n\tclicks (child): {count}\n</button>\n```\n\nWhile you can temporarily _reassign_ props, you should not _mutate_ props unless they are [bindable]($bindable).\n\nIf the prop is a regular object, the mutation will have no effect ([demo](/playground/untitled#H4sIAAAAAAAAE3WQwU7DMBBEf2W1QmorQgJXk0RC3PkBwiExG9WQrC17U4Es_ztKUkQp9OjxzM7bjcjtSKjwyfKNp1aLORA4b13ADHszUED1HFE-3eyaBcy-Mw_O5eFAg8xa1wb6T9eWhVgCKiyD9sZJ3XAjZnTWCzzuzfAKvbcjbPJieR2jm_uGy-InweXqtd0baaliBG0nFgW3kBIUNWYo9CGoxE-UsgvIpw2_oc9-LmAPJBCPDJCggqvlVtvdH9puErEMlvVg9HsVtzuoaojzkKKAfRuALVDfk5ZZW0fmy05wXcFdwyktlUs-KIinljTXrRVnm7-kL9dYLVbUAQAA)):\n\n```svelte\n<!--- file: App.svelte --->\n<script>\n\timport Child from './Child.svelte';\n</script>\n\n<Child object={{ count: 0 }} />\n```\n\n```svelte\n<!--- file: Child.svelte --->\n<script>\n\tlet { object } = $props();\n</script>\n\n<button onclick={() => {\n\t// has no effect\n\tobject.count += 1\n}}>\n\tclicks: {object.count}\n</button>\n```\n\nIf the prop is a reactive state proxy, however, then mutations _will_ have an effect but you will see an [`ownership_invalid_mutation`](runtime-warnings#Client-warnings-ownership_invalid_mutation) warning, because the component is mutating state that does not 'belong' to it ([demo](/playground/untitled#H4sIAAAAAAAAE3WR0U7DMAxFf8VESBuiauG1WycheOEbKA9p67FA6kSNszJV-XeUZhMw2GN8r-1znUmQ7FGU4pn2UqsOes-SlSGRia3S6ET5Mgk-2OiJBZGdOh6szd0eNcdaIx3-V28NMRI7UYq1awdleVNTzaq3ZmB43CndwXYwPSzyYn4dWxermqJRI4Np3rFlqODasWRcTtAaT1zCHYSbVU3r4nsyrdPMKTUFKDYiE4yfLEoePIbsQpqfy3_nOVMuJIqg0wk1RFg7GOuWfwEbz2wIDLVatR_VtLyBagNTHFIUMCqtoZXeIfAOU1JoUJsR2IC3nWTMjt7GM4yKdyBhlAMpesvhydCC0y_i0ZagHByMh26WzUhXUUxKnpbcVnBfUwhznJnNlac7JkuIURL-2VVfwxflyrWcSQIAAA==)):\n\n```svelte\n<!--- file: App.svelte --->\n<script>\n\timport Child from './Child.svelte';\n\n\tlet object = $state({count: 0});\n</script>\n\n<Child {object} />\n```\n\n```svelte\n<!--- file: Child.svelte --->\n<script>\n\tlet { object } = $props();\n</script>\n\n<button onclick={() => {\n\t// will cause the count below to update,\n\t// but with a warning. Don't mutate\n\t// objects you don't own!\n\tobject.count += 1\n}}>\n\tclicks: {object.count}\n</button>\n```\n\nThe fallback value of a prop not declared with `$bindable` is left untouched — it is not turned into a reactive state proxy — meaning mutations will not cause updates ([demo](/playground/untitled#H4sIAAAAAAAAE3WQwU7DMBBEf2VkIbUVoYFraCIh7vwA4eC4G9Wta1vxpgJZ_nfkBEQp9OjxzOzTRGHlkUQlXpy9G0gq1idCL43ppDrAD84HUYheGwqieo2CP3y2Z0EU3-En79fhRIaz1slA_-nKWSbLQVRiE9SgPTetbVkfvRsYzztttugHd8RiXU6vr-jisbWb8idhN7O3bEQhmN5ZVDyMlIorcOddv_Eufq4AGmJEuG5PilEjQrnRcoV7JCTUuJlGWq7-YHYjs7NwVhmtDnVcrlA3iLmzLLGTAdaB-j736h68Oxv-JM1I0AFjoG1OzPfX023c1nhobUoT39QeKsRzS8owM8DFTG_pE6dcVl70AQAA))\n\n```svelte\n<!--- file: Child.svelte --->\n<script>\n\tlet { object = { count: 0 } } = $props();\n</script>\n\n<button onclick={() => {\n\t// has no effect if the fallback value is used\n\tobject.count += 1\n}}>\n\tclicks: {object.count}\n</button>\n```\n\nIn summary: don't mutate props. Either use callback props to communicate changes, or — if parent and child should share the same object — use the [`$bindable`]($bindable) rune.\n\n## Type safety\n\nYou can add type safety to your components by annotating your props, as you would with any other variable declaration. In TypeScript that might look like this...\n\n```svelte\n<script lang=\"ts\">\n\tlet { adjective }: { adjective: string } = $props();\n</script>\n```\n\n...while in JSDoc you can do this:\n\n```svelte\n<script>\n\t/** @type {{ adjective: string }} */\n\tlet { adjective } = $props();\n</script>\n```\n\nYou can, of course, separate the type declaration from the annotation:\n\n```svelte\n<script lang=\"ts\">\n\tinterface Props {\n\t\tadjective: string;\n\t}\n\n\tlet { adjective }: Props = $props();\n</script>\n```\n\n> [!NOTE] Interfaces for native DOM elements are provided in the `svelte/elements` module (see [Typing wrapper components](typescript#Typing-wrapper-components))\n\nAdding types is recommended, as it ensures that people using your component can easily discover which props they should provide.\n\n\n## `$props.id()`\n\nThis rune, added in version 5.20.0, generates an ID that is unique to the current component instance. When hydrating a server-rendered component, the value will be consistent between server and client.\n\nThis is useful for linking elements via attributes like `for` and `aria-labelledby`.\n\n```svelte\n<script>\n\tconst uid = $props.id();\n</script>\n\n<form>\n\t<label for=\"{uid}-firstname\">First Name: </label>\n\t<input id=\"{uid}-firstname\" type=\"text\" />\n\n\t<label for=\"{uid}-lastname\">Last Name: </label>\n\t<input id=\"{uid}-lastname\" type=\"text\" />\n</form>\n```\n\n---\n\n## {#if ...}\n\n```svelte\n<!--- copy: false --->\n{#if expression}...{/if}\n```\n\n```svelte\n<!--- copy: false --->\n{#if expression}...{:else if expression}...{/if}\n```\n\n```svelte\n<!--- copy: false --->\n{#if expression}...{:else}...{/if}\n```\n\nContent that is conditionally rendered can be wrapped in an if block.\n\n```svelte\n{#if answer === 42}\n\t<p>what was the question?</p>\n{/if}\n```\n\nAdditional conditions can be added with `{:else if expression}`, optionally ending in an `{:else}` clause.\n\n```svelte\n{#if porridge.temperature > 100}\n\t<p>too hot!</p>\n{:else if 80 > porridge.temperature}\n\t<p>too cold!</p>\n{:else}\n\t<p>just right!</p>\n{/if}\n```\n\n(Blocks don't have to wrap elements, they can also wrap text within elements.)\n\n---\n\n## Basic markup\n\nMarkup inside a Svelte component can be thought of as HTML++.\n\n## Tags\n\nA lowercase tag, like `<div>`, denotes a regular HTML element. A capitalised tag or a tag that uses dot notation, such as `<Widget>` or `<my.stuff>`, indicates a _component_.\n\n```svelte\n<script>\n\timport Widget from './Widget.svelte';\n</script>\n\n<div>\n\t<Widget />\n</div>\n```\n\n## Element attributes\n\nBy default, attributes work exactly like their HTML counterparts.\n\n```svelte\n<div class=\"foo\">\n\t<button disabled>can't touch this</button>\n</div>\n```\n\nAs in HTML, values may be unquoted.\n\n<!-- prettier-ignore -->\n```svelte\n<input type=checkbox />\n```\n\nAttribute values can contain JavaScript expressions.\n\n```svelte\n<a href=\"page/{p}\">page {p}</a>\n```\n\nOr they can _be_ JavaScript expressions.\n\n```svelte\n<button disabled={!clickable}>...</button>\n```\n\nBoolean attributes are included on the element if their value is [truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy) and excluded if it's [falsy](https://developer.mozilla.org/en-US/docs/Glossary/Falsy).\n\nAll other attributes are included unless their value is [nullish](https://developer.mozilla.org/en-US/docs/Glossary/Nullish) (`null` or `undefined`).\n\n```svelte\n<input required={false} placeholder=\"This input field is not required\" />\n<div title={null}>This div has no title attribute</div>\n```\n\n> [!NOTE] Quoting a singular expression does not affect how the value is parsed, but in Svelte 6 it will cause the value to be coerced to a string:\n>\n> <!-- prettier-ignore -->\n> ```svelte\n> <button disabled=\"{number !== 42}\">...</button>\n> ```\n\nWhen the attribute name and value match (`name={name}`), they can be replaced with `{name}`.\n\n```svelte\n<button {disabled}>...</button>\n<!-- equivalent to\n<button disabled={disabled}>...</button>\n-->\n```\n\n## Component props\n\nBy convention, values passed to components are referred to as _properties_ or _props_ rather than _attributes_, which are a feature of the DOM.\n\nAs with elements, `name={name}` can be replaced with the `{name}` shorthand.\n\n```svelte\n<Widget foo={bar} answer={42} text=\"hello\" />\n```\n\n## Spread attributes\n\n_Spread attributes_ allow many attributes or properties to be passed to an element or component at once.\n\nAn element or component can have multiple spread attributes, interspersed with regular ones. Order matters — if `things.a` exists it will take precedence over `a=\"b\"`, while `c=\"d\"` would take precedence over `things.c`:\n\n```svelte\n<Widget a=\"b\" {...things} c=\"d\" />\n```\n\n## Events\n\nListening to DOM events is possible by adding attributes to the element that start with `on`. For example, to listen to the `click` event, add the `onclick` attribute to a button:\n\n```svelte\n<button onclick={() => console.log('clicked')}>click me</button>\n```\n\nEvent attributes are case sensitive. `onclick` listens to the `click` event, `onClick` listens to the `Click` event, which is different. This ensures you can listen to custom events that have uppercase characters in them.\n\nBecause events are just attributes, the same rules as for attributes apply:\n\n- you can use the shorthand form: `<button {onclick}>click me</button>`\n- you can spread them: `<button {...thisSpreadContainsEventAttributes}>click me</button>`\n\nTiming-wise, event attributes always fire after events from bindings (e.g. `oninput` always fires after an update to `bind:value`). Under the hood, some event handlers are attached directly with `addEventListener`, while others are _delegated_.\n\nWhen using `ontouchstart` and `ontouchmove` event attributes, the handlers are [passive](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#using_passive_listeners) for better performance. This greatly improves responsiveness by allowing the browser to scroll the document immediately, rather than waiting to see if the event handler calls `event.preventDefault()`.\n\nIn the very rare cases that you need to prevent these event defaults, you should use [`on`](svelte-events#on) instead (for example inside an action).\n\n### Event delegation\n\nTo reduce memory footprint and increase performance, Svelte uses a technique called event delegation. This means that for certain events — see the list below — a single event listener at the application root takes responsibility for running any handlers on the event's path.\n\nThere are a few gotchas to be aware of:\n\n- when you manually dispatch an event with a delegated listener, make sure to set the `{ bubbles: true }` option or it won't reach the application root\n- when using `addEventListener` directly, avoid calling `stopPropagation` or the event won't reach the application root and handlers won't be invoked. Similarly, handlers added manually inside the application root will run _before_ handlers added declaratively deeper in the DOM (with e.g. `onclick={...}`), in both capturing and bubbling phases. For these reasons it's better to use the `on` function imported from `svelte/events` rather than `addEventListener`, as it will ensure that order is preserved and `stopPropagation` is handled correctly.\n\nThe following event handlers are delegated:\n\n- `beforeinput`\n- `click`\n- `change`\n- `dblclick`\n- `contextmenu`\n- `focusin`\n- `focusout`\n- `input`\n- `keydown`\n- `keyup`\n- `mousedown`\n- `mousemove`\n- `mouseout`\n- `mouseover`\n- `mouseup`\n- `pointerdown`\n- `pointermove`\n- `pointerout`\n- `pointerover`\n- `pointerup`\n- `touchend`\n- `touchmove`\n- `touchstart`\n\n## Text expressions\n\nA JavaScript expression can be included as text by surrounding it with curly braces.\n\n```svelte\n{expression}\n```\n\nExpressions that are `null` or `undefined` will be omitted; all others are [coerced to strings](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String#string_coercion).\n\nCurly braces can be included in a Svelte template by using their [HTML entity](https://developer.mozilla.org/docs/Glossary/Entity) strings: `{`, `{`, or `{` for `{` and `}`, `}`, or `}` for `}`.\n\nIf you're using a regular expression (`RegExp`) [literal notation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp#literal_notation_and_constructor), you'll need to wrap it in parentheses.\n\n<!-- prettier-ignore -->\n```svelte\n<h1>Hello {name}!</h1>\n<p>{a} + {b} = {a + b}.</p>\n\n<div>{(/^[A-Za-z ]+$/).test(value) ? x : y}</div>\n```\n\nThe expression will be stringified and escaped to prevent code injections. If you want to render HTML, use the `{@html}` tag instead.\n\n```svelte\n{@html potentiallyUnsafeHtmlString}\n```\n\n> [!NOTE] Make sure that you either escape the passed string or only populate it with values that are under your control in order to prevent [XSS attacks](https://owasp.org/www-community/attacks/xss/)\n\n## Comments\n\nYou can use HTML comments inside components.\n\n```svelte\n<!-- this is a comment! --><h1>Hello world</h1>\n```\n\nComments beginning with `svelte-ignore` disable warnings for the next block of markup. Usually, these are accessibility warnings; make sure that you're disabling them for a good reason.\n\n```svelte\n<!-- svelte-ignore a11y_autofocus -->\n<input bind:value={name} autofocus />\n```\n\nYou can add a special comment starting with `@component` that will show up when hovering over the component name in other files.\n\n````svelte\n<!--\n@component\n- You can use markdown here.\n- You can also use code blocks here.\n- Usage:\n ```html\n <Main name=\"Arethra\">\n ```\n-->\n<script>\n\tlet { name } = $props();\n</script>\n\n<main>\n\t<h1>\n\t\tHello, {name}\n\t</h1>\n</main>\n````"
}
],
"isError": false
}
{
"content": "<script>\n\tlet { name = \"World\", count = 0, showDetails = false } = $props();\n\n\tlet localCount = $state(count);\n\n\tfunction increment() {\n\t\tlocalCount++;\n\t}\n</script>\n\n<h1 data-testid=\"name-display\">Hello, {name}!</h1>\n\n<div data-testid=\"count-display\">{localCount}</div>\n\n<button data-testid=\"increment-button\" on:click={increment}>Increment</button>\n\n{#if showDetails}\n\t<div data-testid=\"details\">\n\t\t<p>Name: {name}</p>\n\t\t<p>Count: {localCount}</p>\n\t\t<p>Show Details: {String(showDetails)}</p>\n\t</div>\n{/if}\n"
}
{
"success": true
}
<script>
let { name = "World", count = 0, showDetails = false } = $props();
let localCount = $state(count);
Create a Svelte 5 book list component that uses snippets to render each title.
The component should display a list of book titles using a snippet to render each title. Use a hardcoded array of 3 books with appropriate syntax for Svelte 5 Snippets.
## Test Suite
Your component must pass the following tests:
```ts
import { render, screen } from "@testing-library/svelte";
import { expect, test, describe } from "vitest";
import BookList from "./Component.svelte";
describe("Simple Snippet component", () => {
test("renders the correct number of book titles", () => {
render(BookList);
const bookItems = screen.getAllByTestId("book-item");
expect(bookItems.length).toBe(3);
const bookTitles = screen.getAllByTestId("book-title");
expect(bookTitles.length).toBe(3);
});
test("displays correct book titles", () => {
render(BookList);
const bookTitles = screen.getAllByTestId("book-title");
expect(bookTitles[0]).toHaveTextContent("The Lord of the Rings");
expect(bookTitles[1]).toHaveTextContent("To Kill a Mockingbird");
expect(bookTitles[2]).toHaveTextContent("1984");
});
test("has the correct structure for each book item", () => {
render(BookList);
const bookItems = screen.getAllByTestId("book-item");
bookItems.forEach((item) => {
expect(item.tagName).toBe("LI");
const title = item.querySelector('[data-testid="book-title"]');
expect(title).toBeInTheDocument();
expect(title?.tagName).toBe("SPAN");
});
});
});
```
IMPORTANT: When you have finished implementing the component, use the ResultWrite tool to output your final Svelte component code. Only output the component code itself, no explanations or markdown formatting.
{
"section": "[\"snippets\"]"
}
{
"content": [
{
"type": "text",
"text": "## snippets\n\nError: Section not found.\n\n---\n\nList of available Svelte documentation sections with their intended use cases. The \"use_cases\" field describes WHEN each section would be useful - analyze these carefully to determine which sections match the user's query:\n\n- title: Overview, use_cases: project setup, creating new svelte apps, scaffolding, cli tools, initializing projects, path: cli/overview\n- title: Frequently asked questions, use_cases: project setup, initializing new svelte projects, troubleshooting cli installation, package manager configuration, path: cli/faq\n- title: sv create, use_cases: project setup, starting new sveltekit app, initializing project, creating from playground, choosing project template, path: cli/sv-create\n- title: sv add, use_cases: project setup, adding features to existing projects, integrating tools, testing setup, styling setup, authentication, database setup, deployment adapters, path: cli/sv-add\n- title: sv check, use_cases: code quality, ci/cd pipelines, error checking, typescript projects, pre-commit hooks, finding unused css, accessibility auditing, production builds, path: cli/sv-check\n- title: sv migrate, use_cases: migration, upgrading svelte versions, upgrading sveltekit versions, modernizing codebase, svelte 3 to 4, svelte 4 to 5, sveltekit 1 to 2, adopting runes, refactoring deprecated apis, path: cli/sv-migrate\n- title: devtools-json, use_cases: development setup, chrome devtools integration, browser-based editing, local development workflow, debugging setup, path: cli/devtools-json\n- title: drizzle, use_cases: database setup, sql queries, orm integration, data modeling, postgresql, mysql, sqlite, server-side data access, database migrations, type-safe queries, path: cli/drizzle\n- title: eslint, use_cases: code quality, linting, error detection, project setup, code standards, team collaboration, typescript projects, path: cli/eslint\n- title: lucia, use_cases: authentication, login systems, user management, registration pages, session handling, auth setup, path: cli/lucia\n- title: mcp, use_cases: use title and path to estimate use case, path: cli/mcp\n- title: mdsvex, use_cases: blog, content sites, markdown rendering, documentation sites, technical writing, cms integration, article pages, path: cli/mdsvex\n- title: paraglide, use_cases: internationalization, multi-language sites, i18n, translation, localization, language switching, global apps, multilingual content, path: cli/paraglide\n- title: playwright, use_cases: browser testing, e2e testing, integration testing, test automation, quality assurance, ci/cd pipelines, testing user flows, path: cli/playwright\n- title: prettier, use_cases: code formatting, project setup, code style consistency, team collaboration, linting configuration, path: cli/prettier\n- title: storybook, use_cases: component development, design systems, ui library, isolated component testing, documentation, visual testing, component showcase, path: cli/storybook\n- title: sveltekit-adapter, use_cases: deployment, production builds, hosting setup, choosing deployment platform, configuring adapters, static site generation, node server, vercel, cloudflare, netlify, path: cli/sveltekit-adapter\n- title: tailwindcss, use_cases: project setup, styling, css framework, rapid prototyping, utility-first css, design systems, responsive design, adding tailwind to svelte, path: cli/tailwind\n- title: vitest, use_cases: testing, unit tests, component testing, test setup, quality assurance, ci/cd pipelines, test-driven development, path: cli/vitest\n- title: Introduction, use_cases: learning sveltekit, project setup, understanding framework basics, choosing between svelte and sveltekit, getting started with full-stack apps, path: kit/introduction\n- title: Creating a project, use_cases: project setup, starting new sveltekit app, initial development environment, first-time sveltekit users, scaffolding projects, path: kit/creating-a-project\n- title: Project types, use_cases: deployment, project setup, choosing adapters, ssg, spa, ssr, serverless, mobile apps, desktop apps, pwa, offline apps, browser extensions, separate backend, docker containers, path: kit/project-types\n- title: Project structure, use_cases: project setup, understanding file structure, organizing code, starting new project, learning sveltekit basics, path: kit/project-structure\n- title: Web standards, use_cases: always, any sveltekit project, data fetching, forms, api routes, server-side rendering, deployment to various platforms, path: kit/web-standards\n- title: Routing, use_cases: routing, navigation, multi-page apps, project setup, file structure, api endpoints, data loading, layouts, error pages, always, path: kit/routing\n- title: Loading data, use_cases: data fetching, api calls, database queries, dynamic routes, page initialization, loading states, authentication checks, ssr data, form data, content rendering, path: kit/load\n- title: Form actions, use_cases: forms, user input, data submission, authentication, login systems, user registration, progressive enhancement, validation errors, path: kit/form-actions\n- title: Page options, use_cases: prerendering static sites, ssr configuration, spa setup, client-side rendering control, url trailing slash handling, adapter deployment config, build optimization, path: kit/page-options\n- title: State management, use_cases: sveltekit, server-side rendering, ssr, state management, authentication, data persistence, load functions, context api, navigation, component lifecycle, path: kit/state-management\n- title: Remote functions, use_cases: data fetching, server-side logic, database queries, type-safe client-server communication, forms, user input, mutations, authentication, crud operations, optimistic updates, path: kit/remote-functions\n- title: Building your app, use_cases: production builds, deployment preparation, build process optimization, adapter configuration, preview before deployment, path: kit/building-your-app\n- title: Adapters, use_cases: deployment, production builds, hosting setup, choosing deployment platform, configuring adapters, path: kit/adapters\n- title: Zero-config deployments, use_cases: deployment, production builds, hosting setup, choosing deployment platform, ci/cd configuration, path: kit/adapter-auto\n- title: Node servers, use_cases: deployment, production builds, node.js hosting, custom server setup, environment configuration, reverse proxy setup, docker deployment, systemd services, path: kit/adapter-node\n- title: Static site generation, use_cases: static site generation, ssg, prerendering, deployment, github pages, spa mode, blogs, documentation sites, marketing sites, path: kit/adapter-static\n- title: Single-page apps, use_cases: spa mode, single-page apps, client-only rendering, static hosting, mobile app wrappers, no server-side logic, adapter-static setup, fallback pages, path: kit/single-page-apps\n- title: Cloudflare, use_cases: deployment, cloudflare workers, cloudflare pages, hosting setup, production builds, serverless deployment, edge computing, path: kit/adapter-cloudflare\n- title: Cloudflare Workers, use_cases: deploying to cloudflare workers, cloudflare workers sites deployment, legacy cloudflare adapter, wrangler configuration, cloudflare platform bindings, path: kit/adapter-cloudflare-workers\n- title: Netlify, use_cases: deployment, netlify hosting, production builds, serverless functions, edge functions, static site hosting, path: kit/adapter-netlify\n- title: Vercel, use_cases: deployment, vercel hosting, production builds, serverless functions, edge functions, isr, image optimization, environment variables, path: kit/adapter-vercel\n- title: Writing adapters, use_cases: custom deployment, building adapters, unsupported platforms, adapter development, custom hosting environments, path: kit/writing-adapters\n- title: Advanced routing, use_cases: advanced routing, dynamic routes, file viewers, nested paths, custom 404 pages, url validation, route parameters, multi-level navigation, path: kit/advanced-routing\n- title: Hooks, use_cases: authentication, logging, error tracking, request interception, api proxying, custom routing, internationalization, database initialization, middleware logic, session management, path: kit/hooks\n- title: Errors, use_cases: error handling, custom error pages, 404 pages, api error responses, production error logging, error tracking, type-safe errors, path: kit/errors\n- title: Link options, use_cases: routing, navigation, multi-page apps, performance optimization, link preloading, forms with get method, search functionality, focus management, scroll behavior, path: kit/link-options\n- title: Service workers, use_cases: offline support, pwa, caching strategies, performance optimization, precaching assets, network resilience, progressive web apps, path: kit/service-workers\n- title: Server-only modules, use_cases: api keys, environment variables, sensitive data protection, backend security, preventing data leaks, server-side code isolation, path: kit/server-only-modules\n- title: Snapshots, use_cases: forms, user input, preserving form data, multi-step forms, navigation state, preventing data loss, textarea content, input fields, comment systems, surveys, path: kit/snapshots\n- title: Shallow routing, use_cases: modals, dialogs, image galleries, overlays, history-driven ui, mobile-friendly navigation, photo viewers, lightboxes, drawer menus, path: kit/shallow-routing\n- title: Observability, use_cases: performance monitoring, debugging, observability, tracing requests, production diagnostics, analyzing slow requests, finding bottlenecks, monitoring server-side operations, path: kit/observability\n- title: Packaging, use_cases: building component libraries, publishing npm packages, creating reusable svelte components, library development, package distribution, path: kit/packaging\n- title: Auth, use_cases: authentication, login systems, user management, session handling, jwt tokens, protected routes, user credentials, authorization checks, path: kit/auth\n- title: Performance, use_cases: performance optimization, slow loading pages, production deployment, debugging performance issues, reducing bundle size, improving load times, path: kit/performance\n- title: Icons, use_cases: icons, ui components, styling, css frameworks, tailwind, unocss, performance optimization, dependency management, path: kit/icons\n- title: Images, use_cases: image optimization, responsive images, performance, hero images, product photos, galleries, cms integration, cdn setup, asset management, path: kit/images\n- title: Accessibility, use_cases: always, any sveltekit project, screen reader support, keyboard navigation, multi-page apps, client-side routing, internationalization, multilingual sites, path: kit/accessibility\n- title: SEO, use_cases: seo optimization, search engine ranking, content sites, blogs, marketing sites, public-facing apps, sitemaps, amp pages, meta tags, performance optimization, path: kit/seo\n- title: Frequently asked questions, use_cases: troubleshooting package imports, library compatibility issues, client-side code execution, external api integration, middleware setup, database configuration, view transitions, yarn configuration, path: kit/faq\n- title: Integrations, use_cases: project setup, css preprocessors, postcss, scss, sass, less, stylus, typescript setup, adding integrations, tailwind, testing, auth, linting, formatting, path: kit/integrations\n- title: Breakpoint Debugging, use_cases: debugging, breakpoints, development workflow, troubleshooting issues, vscode setup, ide configuration, inspecting code execution, path: kit/debugging\n- title: Migrating to SvelteKit v2, use_cases: migration, upgrading from sveltekit 1 to 2, breaking changes, version updates, path: kit/migrating-to-sveltekit-2\n- title: Migrating from Sapper, use_cases: migrating from sapper, upgrading legacy projects, sapper to sveltekit conversion, project modernization, path: kit/migrating\n- title: Additional resources, use_cases: troubleshooting, getting help, finding examples, learning sveltekit, project templates, common issues, community support, path: kit/additional-resources\n- title: Glossary, use_cases: rendering strategies, performance optimization, deployment configuration, seo requirements, static sites, spas, server-side rendering, prerendering, edge deployment, pwa development, path: kit/glossary\n- title: @sveltejs/kit, use_cases: forms, form actions, server-side validation, form submission, error handling, redirects, json responses, http errors, server utilities, path: kit/@sveltejs-kit\n- title: @sveltejs/kit/hooks, use_cases: middleware, request processing, authentication chains, logging, multiple hooks, request/response transformation, path: kit/@sveltejs-kit-hooks\n- title: @sveltejs/kit/node/polyfills, use_cases: node.js environments, custom servers, non-standard runtimes, ssr setup, web api compatibility, polyfill requirements, path: kit/@sveltejs-kit-node-polyfills\n- title: @sveltejs/kit/node, use_cases: node.js adapter, custom server setup, http integration, streaming files, node deployment, server-side rendering with node, path: kit/@sveltejs-kit-node\n- title: @sveltejs/kit/vite, use_cases: project setup, vite configuration, initial sveltekit setup, build tooling, path: kit/@sveltejs-kit-vite\n- title: $app/environment, use_cases: always, conditional logic, client-side code, server-side code, build-time logic, prerendering, development vs production, environment detection, path: kit/$app-environment\n- title: $app/forms, use_cases: forms, user input, data submission, progressive enhancement, custom form handling, form validation, path: kit/$app-forms\n- title: $app/navigation, use_cases: routing, navigation, multi-page apps, programmatic navigation, data reloading, preloading, shallow routing, navigation lifecycle, scroll handling, view transitions, path: kit/$app-navigation\n- title: $app/paths, use_cases: static assets, images, fonts, public files, base path configuration, subdirectory deployment, cdn setup, asset urls, links, navigation, path: kit/$app-paths\n- title: $app/server, use_cases: remote functions, server-side logic, data fetching, form handling, api endpoints, client-server communication, prerendering, file reading, batch queries, path: kit/$app-server\n- title: $app/state, use_cases: routing, navigation, multi-page apps, loading states, url parameters, form handling, error states, version updates, page metadata, shallow routing, path: kit/$app-state\n- title: $app/stores, use_cases: legacy projects, sveltekit pre-2.12, migration from stores to runes, maintaining older codebases, accessing page data, navigation state, app version updates, path: kit/$app-stores\n- title: $app/types, use_cases: routing, navigation, type safety, route parameters, dynamic routes, link generation, pathname validation, multi-page apps, path: kit/$app-types\n- title: $env/dynamic/private, use_cases: api keys, secrets management, server-side config, environment variables, backend logic, deployment-specific settings, private data handling, path: kit/$env-dynamic-private\n- title: $env/dynamic/public, use_cases: environment variables, client-side config, runtime configuration, public api keys, deployment-specific settings, multi-environment apps, path: kit/$env-dynamic-public\n- title: $env/static/private, use_cases: server-side api keys, backend secrets, database credentials, private configuration, build-time optimization, server endpoints, authentication tokens, path: kit/$env-static-private\n- title: $env/static/public, use_cases: environment variables, public config, client-side data, api endpoints, build-time configuration, public constants, path: kit/$env-static-public\n- title: $lib, use_cases: project setup, component organization, importing shared components, reusable ui elements, code structure, path: kit/$lib\n- title: $service-worker, use_cases: offline support, pwa, service workers, caching strategies, progressive web apps, offline-first apps, path: kit/$service-worker\n- title: Configuration, use_cases: project setup, configuration, adapters, deployment, build settings, environment variables, routing customization, prerendering, csp security, csrf protection, path configuration, typescript setup, path: kit/configuration\n- title: Command Line Interface, use_cases: project setup, typescript configuration, generated types, ./$types imports, initial project configuration, path: kit/cli\n- title: Types, use_cases: typescript, type safety, route parameters, api endpoints, load functions, form actions, generated types, jsconfig setup, path: kit/types\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/overview\n- title: Local setup, use_cases: use title and path to estimate use case, path: mcp/local-setup\n- title: Remote setup, use_cases: use title and path to estimate use case, path: mcp/remote-setup\n- title: Tools, use_cases: use title and path to estimate use case, path: mcp/tools\n- title: Resources, use_cases: use title and path to estimate use case, path: mcp/resources\n- title: Prompts, use_cases: use title and path to estimate use case, path: mcp/prompts\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/plugin\n- title: Skill, use_cases: use title and path to estimate use case, path: mcp/skill\n- title: Subagent, use_cases: use title and path to estimate use case, path: mcp/subagent\n- title: Overview, use_cases: use title and path to estimate use case, path: mcp/opencode-plugin\n- title: Subagent, use_cases: use title and path to estimate use case, path: mcp/opencode-subagent\n- title: Overview, use_cases: always, any svelte project, getting started, learning svelte, introduction, project setup, understanding framework basics, path: svelte/overview\n- title: Getting started, use_cases: project setup, starting new svelte project, initial installation, choosing between sveltekit and vite, editor configuration, path: svelte/getting-started\n- title: .svelte files, use_cases: always, any svelte project, component creation, project setup, learning svelte basics, path: svelte/svelte-files\n- title: .svelte.js and .svelte.ts files, use_cases: shared reactive state, reusable reactive logic, state management across components, global stores, custom reactive utilities, path: svelte/svelte-js-files\n- title: What are runes?, use_cases: always, any svelte 5 project, understanding core syntax, learning svelte 5, migration from svelte 4, path: svelte/what-are-runes\n- title: $state, use_cases: always, any svelte project, core reactivity, state management, counters, forms, todo apps, interactive ui, data updates, class-based components, path: svelte/$state\n- title: $derived, use_cases: always, any svelte project, computed values, reactive calculations, derived data, transforming state, dependent values, path: svelte/$derived\n- title: $effect, use_cases: canvas drawing, third-party library integration, dom manipulation, side effects, intervals, timers, network requests, analytics tracking, path: svelte/$effect\n- title: $props, use_cases: always, any svelte project, passing data to components, component communication, reusable components, component props, path: svelte/$props\n- title: $bindable, use_cases: forms, user input, two-way data binding, custom input components, parent-child communication, reusable form fields, path: svelte/$bindable\n- title: $inspect, use_cases: debugging, development, tracking state changes, reactive state monitoring, troubleshooting reactivity issues, path: svelte/$inspect\n- title: $host, use_cases: custom elements, web components, dispatching custom events, component library, framework-agnostic components, path: svelte/$host\n- title: Basic markup, use_cases: always, any svelte project, basic markup, html templating, component structure, attributes, events, props, text rendering, path: svelte/basic-markup\n- title: {#if ...}, use_cases: always, conditional rendering, showing/hiding content, dynamic ui, user permissions, loading states, error handling, form validation, path: svelte/if\n- title: {#each ...}, use_cases: always, lists, arrays, iteration, product listings, todos, tables, grids, dynamic content, shopping carts, user lists, comments, feeds, path: svelte/each\n- title: {#key ...}, use_cases: animations, transitions, component reinitialization, forcing component remount, value-based ui updates, resetting component state, path: svelte/key\n- title: {#await ...}, use_cases: async data fetching, api calls, loading states, promises, error handling, lazy loading components, dynamic imports, path: svelte/await\n- title: {#snippet ...}, use_cases: reusable markup, component composition, passing content to components, table rows, list items, conditional rendering, reducing duplication, path: svelte/snippet\n- title: {@render ...}, use_cases: reusable ui patterns, component composition, conditional rendering, fallback content, layout components, slot alternatives, template reuse, path: svelte/@render\n- title: {@html ...}, use_cases: rendering html strings, cms content, rich text editors, markdown to html, blog posts, wysiwyg output, sanitized html injection, dynamic html content, path: svelte/@html\n- title: {@attach ...}, use_cases: tooltips, popovers, dom manipulation, third-party libraries, canvas drawing, element lifecycle, interactive ui, custom directives, wrapper components, path: svelte/@attach\n- title: {@const ...}, use_cases: computed values in loops, derived calculations in blocks, local variables in each iterations, complex list rendering, path: svelte/@const\n- title: {@debug ...}, use_cases: debugging, development, troubleshooting, tracking state changes, monitoring variables, reactive data inspection, path: svelte/@debug\n- title: bind:, use_cases: forms, user input, two-way data binding, interactive ui, media players, file uploads, checkboxes, radio buttons, select dropdowns, contenteditable, dimension tracking, path: svelte/bind\n- title: use:, use_cases: custom directives, dom manipulation, third-party library integration, tooltips, click outside, gestures, focus management, element lifecycle hooks, path: svelte/use\n- title: transition:, use_cases: animations, interactive ui, modals, dropdowns, notifications, conditional content, show/hide elements, smooth state changes, path: svelte/transition\n- title: in: and out:, use_cases: animation, transitions, interactive ui, conditional rendering, independent enter/exit effects, modals, tooltips, notifications, path: svelte/in-and-out\n- title: animate:, use_cases: sortable lists, drag and drop, reorderable items, todo lists, kanban boards, playlist editors, priority queues, animated list reordering, path: svelte/animate\n- title: style:, use_cases: dynamic styling, conditional styles, theming, dark mode, responsive design, interactive ui, component styling, path: svelte/style\n- title: class, use_cases: always, conditional styling, dynamic classes, tailwind css, component styling, reusable components, responsive design, path: svelte/class\n- title: await, use_cases: async data fetching, loading states, server-side rendering, awaiting promises in components, async validation, concurrent data loading, path: svelte/await-expressions\n- title: Scoped styles, use_cases: always, styling components, scoped css, component-specific styles, preventing style conflicts, animations, keyframes, path: svelte/scoped-styles\n- title: Global styles, use_cases: global styles, third-party libraries, css resets, animations, styling body/html, overriding component styles, shared keyframes, base styles, path: svelte/global-styles\n- title: Custom properties, use_cases: theming, custom styling, reusable components, design systems, dynamic colors, component libraries, ui customization, path: svelte/custom-properties\n- title: Nested <style> elements, use_cases: component styling, scoped styles, dynamic styles, conditional styling, nested style tags, custom styling logic, path: svelte/nested-style-elements\n- title: <svelte:boundary>, use_cases: error handling, async data loading, loading states, error recovery, flaky components, error reporting, resilient ui, path: svelte/svelte-boundary\n- title: <svelte:window>, use_cases: keyboard shortcuts, scroll tracking, window resize handling, responsive layouts, online/offline detection, viewport dimensions, global event listeners, path: svelte/svelte-window\n- title: <svelte:document>, use_cases: document events, visibility tracking, fullscreen detection, pointer lock, focus management, document-level interactions, path: svelte/svelte-document\n- title: <svelte:body>, use_cases: mouse tracking, hover effects, cursor interactions, global body events, drag and drop, custom cursors, interactive backgrounds, body-level actions, path: svelte/svelte-body\n- title: <svelte:head>, use_cases: seo optimization, page titles, meta tags, social media sharing, dynamic head content, multi-page apps, blog posts, product pages, path: svelte/svelte-head\n- title: <svelte:element>, use_cases: dynamic content, cms integration, user-generated content, configurable ui, runtime element selection, flexible components, path: svelte/svelte-element\n- title: <svelte:options>, use_cases: migration, custom elements, web components, legacy mode compatibility, runes mode setup, svg components, mathml components, css injection control, path: svelte/svelte-options\n- title: Stores, use_cases: shared state, cross-component data, reactive values, async data streams, manual control over updates, rxjs integration, extracting logic, path: svelte/stores\n- title: Context, use_cases: shared state, avoiding prop drilling, component communication, theme providers, user context, authentication state, configuration sharing, deeply nested components, path: svelte/context\n- title: Lifecycle hooks, use_cases: component initialization, cleanup tasks, timers, subscriptions, dom measurements, chat windows, autoscroll features, migration from svelte 4, path: svelte/lifecycle-hooks\n- title: Imperative component API, use_cases: project setup, client-side rendering, server-side rendering, ssr, hydration, testing, programmatic component creation, tooltips, dynamic mounting, path: svelte/imperative-component-api\n- title: Hydratable data, use_cases: use title and path to estimate use case, path: svelte/hydratable\n- title: Testing, use_cases: testing, quality assurance, unit tests, integration tests, component tests, e2e tests, vitest setup, playwright setup, test automation, path: svelte/testing\n- title: TypeScript, use_cases: typescript setup, type safety, component props typing, generic components, wrapper components, dom type augmentation, project configuration, path: svelte/typescript\n- title: Custom elements, use_cases: web components, custom elements, component library, design system, framework-agnostic components, embedding svelte in non-svelte apps, shadow dom, path: svelte/custom-elements\n- title: Svelte 4 migration guide, use_cases: upgrading svelte 3 to 4, version migration, updating dependencies, breaking changes, legacy project maintenance, path: svelte/v4-migration-guide\n- title: Svelte 5 migration guide, use_cases: migrating from svelte 4 to 5, upgrading projects, learning svelte 5 syntax changes, runes migration, event handler updates, path: svelte/v5-migration-guide\n- title: Frequently asked questions, use_cases: getting started, learning svelte, beginner setup, project initialization, vs code setup, formatting, testing, routing, mobile apps, troubleshooting, community support, path: svelte/faq\n- title: svelte, use_cases: migration from svelte 4 to 5, upgrading legacy code, component lifecycle hooks, context api, mounting components, event dispatchers, typescript component types, path: svelte/svelte\n- title: svelte/action, use_cases: typescript types, actions, use directive, dom manipulation, element lifecycle, custom behaviors, third-party library integration, path: svelte/svelte-action\n- title: svelte/animate, use_cases: animated lists, sortable items, drag and drop, reordering elements, todo lists, kanban boards, playlist management, smooth position transitions, path: svelte/svelte-animate\n- title: svelte/attachments, use_cases: library development, component libraries, programmatic element manipulation, migrating from actions to attachments, spreading props onto elements, path: svelte/svelte-attachments\n- title: svelte/compiler, use_cases: build tools, custom compilers, ast manipulation, preprocessors, code transformation, migration scripts, syntax analysis, bundler plugins, dev tools, path: svelte/svelte-compiler\n- title: svelte/easing, use_cases: animations, transitions, custom easing, smooth motion, interactive ui, modals, dropdowns, carousels, page transitions, scroll effects, path: svelte/svelte-easing\n- title: svelte/events, use_cases: window events, document events, global event listeners, event delegation, programmatic event handling, cleanup functions, media queries, path: svelte/svelte-events\n- title: svelte/legacy, use_cases: migration from svelte 4 to svelte 5, upgrading legacy code, event modifiers, class components, imperative component instantiation, path: svelte/svelte-legacy\n- title: svelte/motion, use_cases: animation, smooth transitions, interactive ui, sliders, counters, physics-based motion, drag gestures, accessibility, reduced motion, path: svelte/svelte-motion\n- title: svelte/reactivity/window, use_cases: responsive design, viewport tracking, scroll effects, window resize handling, online/offline detection, zoom level tracking, path: svelte/svelte-reactivity-window\n- title: svelte/reactivity, use_cases: reactive data structures, state management with maps/sets, game boards, selection tracking, url manipulation, query params, real-time clocks, media queries, responsive design, path: svelte/svelte-reactivity\n- title: svelte/server, use_cases: server-side rendering, ssr, static site generation, seo optimization, initial page load, pre-rendering, node.js server, custom server setup, path: svelte/svelte-server\n- title: svelte/store, use_cases: state management, shared data, reactive stores, cross-component communication, global state, computed values, data synchronization, legacy svelte projects, path: svelte/svelte-store\n- title: svelte/transition, use_cases: animations, transitions, interactive ui, modals, dropdowns, tooltips, notifications, svg animations, list animations, page transitions, path: svelte/svelte-transition\n- title: Compiler errors, use_cases: animation, transitions, keyed each blocks, list animations, path: svelte/compiler-errors\n- title: Compiler warnings, use_cases: accessibility, a11y compliance, wcag standards, screen readers, keyboard navigation, aria attributes, semantic html, interactive elements, path: svelte/compiler-warnings\n- title: Runtime errors, use_cases: debugging errors, error handling, troubleshooting runtime issues, migration to svelte 5, component binding, effects and reactivity, path: svelte/runtime-errors\n- title: Runtime warnings, use_cases: debugging state proxies, console logging reactive values, inspecting state changes, development troubleshooting, path: svelte/runtime-warnings\n- title: Overview, use_cases: migrating from svelte 3/4 to svelte 5, maintaining legacy components, understanding deprecated features, gradual upgrade process, path: svelte/legacy-overview\n- title: Reactive let/var declarations, use_cases: migration, legacy svelte projects, upgrading from svelte 4, understanding old reactivity, maintaining existing code, learning runes differences, path: svelte/legacy-let\n- title: Reactive $: statements, use_cases: legacy mode, migration from svelte 4, reactive statements, computed values, derived state, side effects, path: svelte/legacy-reactive-assignments\n- title: export let, use_cases: legacy mode, migration from svelte 4, maintaining older projects, component props without runes, exporting component methods, renaming reserved word props, path: svelte/legacy-export-let\n- title: $$props and $$restProps, use_cases: legacy mode migration, component wrappers, prop forwarding, button components, reusable ui components, spreading props to child elements, path: svelte/legacy-$$props-and-$$restProps\n- title: on:, use_cases: legacy mode, event handling, button clicks, forms, user interactions, component communication, event forwarding, event modifiers, path: svelte/legacy-on\n- title: <slot>, use_cases: legacy mode, migrating from svelte 4, component composition, reusable components, passing content to components, modals, layouts, wrappers, path: svelte/legacy-slots\n- title: $$slots, use_cases: legacy mode, conditional slot rendering, optional content sections, checking if slots provided, migrating from legacy to runes, path: svelte/legacy-$$slots\n- title: <svelte:fragment>, use_cases: named slots, component composition, layout systems, avoiding wrapper divs, legacy svelte projects, slot content organization, path: svelte/legacy-svelte-fragment\n- title: <svelte:component>, use_cases: dynamic components, component switching, conditional rendering, legacy mode migration, tabbed interfaces, multi-step forms, path: svelte/legacy-svelte-component\n- title: <svelte:self>, use_cases: recursive components, tree structures, nested menus, file explorers, comment threads, hierarchical data, path: svelte/legacy-svelte-self\n- title: Imperative component API, use_cases: migration from svelte 3/4 to 5, legacy component api, maintaining old projects, understanding deprecated patterns, path: svelte/legacy-component-api\n\nCarefully analyze the use_cases field for each section to identify which documentation is relevant for the user's specific query. The use_cases contain keywords for project types, features, components, and development stages. After identifying relevant sections, use the get-documentation tool with ALL relevant section titles or paths at once (can pass multiple sections as an array)."
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"text": "## {#snippet ...}\n\n```svelte\n<!--- copy: false --->\n{#snippet name()}...{/snippet}\n```\n\n```svelte\n<!--- copy: false --->\n{#snippet name(param1, param2, paramN)}...{/snippet}\n```\n\nSnippets, and [render tags](@render), are a way to create reusable chunks of markup inside your components. Instead of writing duplicative code like [this](/playground/untitled#H4sIAAAAAAAAE5VUYW-kIBD9K8Tmsm2yXXRzvQ-s3eR-R-0HqqOQKhAZb9sz_vdDkV1t000vRmHewMx7w2AflbIGG7GnPlK8gYhFv42JthG-m9Gwf6BGcLbVXZuPSGrzVho8ZirDGpDIhldgySN5GpEMez9kaNuckY1ANJZRamRuu2ZnhEZt6a84pvs43mzD4pMsUDDi8DMkQFYCGdkvsJwblFq5uCik9bmJ4JZwUkv1eoknWigX2eGNN6aGXa6bjV8ybP-X7sM36T58SVcrIIV2xVIaA41xeD5kKqWXuqpUJEefOqVuOkL9DfBchGrzWfu0vb-RpTd3o-zBR045Ga3HfuE5BmJpKauuhbPtENlUF2sqR9jqpsPSxWsMrlngyj3VJiyYjJXb1-lMa7IWC-iSk2M5Zzh-SJjShe-siq5kpZRPs55BbSGU5YPyte4vVV_VfFXxVb10dSLf17pS2lM5HnpPxw4Zpv6x-F57p0jI3OKlVnhv5V9wPQrNYQQ9D_f6aGHlC89fq1Z3qmDkJCTCweOGF4VUFSPJvD_DhreVdA0eu8ehJJ5x91dBaBkpWm3ureCFPt3uzRv56d4kdp-2euG38XZ6dsnd3ZmPG9yRBCrzRUvi-MccOdwz3qE-fOZ7AwAhlrtTUx3c76vRhSwlFBHDtoPhefgHX3dM0PkEAAA=)...\n\n```svelte\n{#each images as image}\n\t{#if image.href}\n\t\t<a href={image.href}>\n\t\t\t<figure>\n\t\t\t\t<img src={image.src} alt={image.caption} width={image.width} height={image.height} />\n\t\t\t\t<figcaption>{image.caption}</figcaption>\n\t\t\t</figure>\n\t\t</a>\n\t{:else}\n\t\t<figure>\n\t\t\t<img src={image.src} alt={image.caption} width={image.width} height={image.height} />\n\t\t\t<figcaption>{image.caption}</figcaption>\n\t\t</figure>\n\t{/if}\n{/each}\n```\n\n...you can write [this](/playground/untitled#H4sIAAAAAAAAE5VUYW-bMBD9KxbRlERKY4jWfSA02n5H6QcXDmwVbMs-lnaI_z6D7TTt1moTAnPvzvfenQ_GpBEd2CS_HxPJekjy5IfWyS7BFz0b9id0CM62ajDVjBS2MkLjqZQldoBE9KwFS-7I_YyUOPqlRGuqnKw5orY5pVpUduj3mitUln5LU3pI0_UuBp9FjTwnDr9AHETLMSeHK6xiGoWSLi9yYT034cwSRjohn17zcQPNFTs8s153sK9Uv_Yh0-5_5d7-o9zbD-UqCaRWrllSYZQxLw_HUhb0ta-y4NnJUxfUvc7QuLJSaO0a3oh2MLBZat8u-wsPnXzKQvTtVVF34xK5d69ThFmHEQ4SpzeVRediTG8rjD5vBSeN3E5JyHh6R1DQK9-iml5kjzQUN_lSgVU8DhYLx7wwjSvRkMDvTjiwF4zM1kXZ7DlF1eN3A7IG85e-zRrYEjjm0FkI4Cc7Ripm0pHOChexhcWXzreeZyRMU6Mk3ljxC9w4QH-cQZ_b3T5pjHxk1VNr1CDrnJy5QDh6XLO6FrLNSRb2l9gz0wo3S6m7HErSgLsPGMHkpDZK31jOanXeHPQz-eruLHUP0z6yTbpbrn223V70uMXNSpQSZjpL0y8hcxxpNqA6_ql3BQAxlxvfpQ_uT9GrWjQC6iRHM8D0MP0GQsIi92QEAAA=):\n\n```svelte\n{#snippet figure(image)}\n\t<figure>\n\t\t<img src={image.src} alt={image.caption} width={image.width} height={image.height} />\n\t\t<figcaption>{image.caption}</figcaption>\n\t</figure>\n{/snippet}\n\n{#each images as image}\n\t{#if image.href}\n\t\t<a href={image.href}>\n\t\t\t{@render figure(image)}\n\t\t</a>\n\t{:else}\n\t\t{@render figure(image)}\n\t{/if}\n{/each}\n```\n\nLike function declarations, snippets can have an arbitrary number of parameters, which can have default values, and you can destructure each parameter. You cannot use rest parameters, however.\n\n## Snippet scope\n\nSnippets can be declared anywhere inside your component. They can reference values declared outside themselves, for example in the `<script>` tag or in `{#each ...}` blocks ([demo](/playground/untitled#H4sIAAAAAAAAE12P0QrCMAxFfyWrwhSEvc8p-h1OcG5RC10bmkyQ0n-3HQPBx3vCPUmCemiDrOpLULYbUdXqTKR2Sj6UA7_RCKbMbvJ9Jg33XpMcW9uKQYEAIzJ3T4QD3LSUDE-PnYA4YET4uOkGMc3W5B3xZrtvbVP9HDas2GqiZHqhMW6Tr9jGbG_oOCMImcUCwrIpFk1FqRyqpRpn0cmjHdAvnrIzuscyq_4nd3dPPD01ukE_NA6qFj9hvMYvGjJADw8BAAA=))...\n\n```svelte\n<script>\n\tlet { message = `it's great to see you!` } = $props();\n</script>\n\n{#snippet hello(name)}\n\t<p>hello {name}! {message}!</p>\n{/snippet}\n\n{@render hello('alice')}\n{@render hello('bob')}\n```\n\n...and they are 'visible' to everything in the same lexical scope (i.e. siblings, and children of those siblings):\n\n```svelte\n<div>\n\t{#snippet x()}\n\t\t{#snippet y()}...{/snippet}\n\n\t\t<!-- this is fine -->\n\t\t{@render y()}\n\t{/snippet}\n\n\t<!-- this will error, as `y` is not in scope -->\n\t{@render y()}\n</div>\n\n<!-- this will also error, as `x` is not in scope -->\n{@render x()}\n```\n\nSnippets can reference themselves and each other ([demo](/playground/untitled#H4sIAAAAAAAAE2WPTQqDMBCFrxLiRqH1Zysi7TlqF1YnENBJSGJLCYGeo5tesUeosfYH3c2bee_jjaWMd6BpfrAU6x5oTvdS0g01V-mFPkNnYNRaDKrxGxto5FKCIaeu1kYwFkauwsoUWtZYPh_3W5FMY4U2mb3egL9kIwY0rbhgiO-sDTgjSEqSTvIDs-jiOP7i_MHuFGAL6p9BtiSbOTl0GtzCuihqE87cqtyam6WRGz_vRcsZh5bmRg3gju4Fptq_kzQBAAA=)):\n\n```svelte\n{#snippet blastoff()}\n\t<span>🚀</span>\n{/snippet}\n\n{#snippet countdown(n)}\n\t{#if n > 0}\n\t\t<span>{n}...</span>\n\t\t{@render countdown(n - 1)}\n\t{:else}\n\t\t{@render blastoff()}\n\t{/if}\n{/snippet}\n\n{@render countdown(10)}\n```\n\n## Passing snippets to components\n\n### Explicit props\n\nWithin the template, snippets are values just like any other. As such, they can be passed to components as props ([demo](/playground/untitled#H4sIAAAAAAAAE3VS247aMBD9lZGpBGwDASRegonaPvQL2qdlH5zYEKvBNvbQLbL875VzAcKyj3PmzJnLGU8UOwqSkd8KJdaCk4TsZS0cyV49wYuJuQiQpGd-N2bu_ooaI1YwJ57hpVYoFDqSEepKKw3mO7VDeTTaIvxiRS1gb_URxvO0ibrS8WanIrHUyiHs7Vmigy28RmyHHmKvDMbMmFq4cQInvGSwTsBYWYoMVhCSB2rBFFPsyl0uruTlR3JZCWvlTXl1Yy_mawiR_rbZKZrellJ-5JQ0RiBUgnFhJ9OGR7HKmwVoilXeIye8DOJGfYCgRlZ3iE876TBsZPX7hPdteO75PC4QaIo8vwNPePmANQ2fMeEFHrLD7rR1jTNkW986E8C3KwfwVr8HSHOSEBT_kGRozyIkn_zQveXDL3rIfPJHtUDwzShJd_Qk3gQCbOGLsdq4yfTRJopRuin3I7nv6kL7ARRjmLdBDG3uv1mhuLA3V2mKtqNEf_oCn8p9aN-WYqH5peP4kWBl1UwJzAEPT9U7K--0fRrrWnPTXpCm1_EVdXjpNmlA8G1hPPyM1fKgMqjFHjctXGjLhZ05w0qpDhksGrybuNEHtJnCalZWsuaTlfq6nPaaBSv_HKw-K57BjzOiVj9ZKQYKzQjZodYFqydYTRN4gPhVzTDO2xnma3HsVWjaLjT8nbfwHy7Q5f2dBAAA)):\n\n```svelte\n<script>\n\timport Table from './Table.svelte';\n\n\tconst fruits = [\n\t\t{ name: 'apples', qty: 5, price: 2 },\n\t\t{ name: 'bananas', qty: 10, price: 1 },\n\t\t{ name: 'cherries', qty: 20, price: 0.5 }\n\t];\n</script>\n\n{#snippet header()}\n\t<th>fruit</th>\n\t<th>qty</th>\n\t<th>price</th>\n\t<th>total</th>\n{/snippet}\n\n{#snippet row(d)}\n\t<td>{d.name}</td>\n\t<td>{d.qty}</td>\n\t<td>{d.price}</td>\n\t<td>{d.qty * d.price}</td>\n{/snippet}\n\n<Table data={fruits} {header} {row} />\n```\n\nThink about it like passing content instead of data to a component. The concept is similar to slots in web components.\n\n### Implicit props\n\nAs an authoring convenience, snippets declared directly _inside_ a component implicitly become props _on_ the component ([demo](/playground/untitled#H4sIAAAAAAAAE3VSTa_aMBD8Kyu_SkAbCA-JSzBR20N_QXt6vIMTO8SqsY29tI2s_PcqTiB8vaPHs7MzuxuIZgdBMvJLo0QlOElIJZXwJHsLBBvb_XUASc7Mb9Yu_B-hsMMK5sUzvDQahUZPMkJ96aTFfKd3KA_WOISfrFACKmcOMFmk8TWUTjY73RFLoz1C5U4SPWzhrcN2GKDrlcGEWauEnyRwxCaDdQLWyVJksII2uaMWTDPNLtzX5YX8-kgua-GcHJVXI3u5WEPb0d83O03TMZSmfRzOkG1Db7mNacOL19JagVALxoWbztq-H8U6j0SaYp2P2BGbOyQ2v8PQIFMXLKRDk177pq0zf6d8bMrzwBdd0pamyPMb-IjNEzS2f86Gz_Dwf-2F9nvNSUJQ_EOSoTuJNvngqK5v4Pas7n4-OCwlEEJcQTIMO-nSQwtb-GSdsX46e9gbRoP9yGQ11I0rEuycunu6PHx1QnPhxm3SFN15MOlYEFJZtf0dUywMbwZOeBGsrKNLYB54-1R9WNqVdki7usim6VmQphf7mnpshiQRhNAXdoOfMyX3OgMlKtz0cGEcF27uLSul3mewjPjgOOoDukxjPS9rqfh0pb-8zs6aBSt_7505aZ7B9xOi0T9YKW4UooVsr0zB1BTrWQJ3EL-oWcZ572GxFoezCk37QLe3897-B2i2U62uBAAA)):\n\n```svelte\n<!-- this is semantically the same as the above -->\n<Table data={fruits}>\n\t{#snippet header()}\n\t\t<th>fruit</th>\n\t\t<th>qty</th>\n\t\t<th>price</th>\n\t\t<th>total</th>\n\t{/snippet}\n\n\t{#snippet row(d)}\n\t\t<td>{d.name}</td>\n\t\t<td>{d.qty}</td>\n\t\t<td>{d.price}</td>\n\t\t<td>{d.qty * d.price}</td>\n\t{/snippet}\n</Table>\n```\n\n### Implicit `children` snippet\n\nAny content inside the component tags that is _not_ a snippet declaration implicitly becomes part of the `children` snippet ([demo](/playground/untitled#H4sIAAAAAAAAE3WOQQrCMBBFrzIMggql3ddY1Du4si5sOmIwnYRkFKX07lKqglqX8_7_w2uRDw1hjlsWI5ZqTPBoLEXMdy3K3fdZDzB5Ndfep_FKVnpWHSKNce1YiCVijirqYLwUJQOYxrsgsLmIOIZjcA1M02w4n-PpomSVvTclqyEutDX6DA2pZ7_ABIVugrmEC3XJH92P55_G39GodCmWBFrQJ2PrQAwdLGHig_NxNv9xrQa1dhWIawrv1Wzeqawa8953D-8QOmaEAQAA)):\n\n```svelte\n<!--- file: App.svelte --->\n<Button>click me</Button>\n```\n\n```svelte\n<!--- file: Button.svelte --->\n<script>\n\tlet { children } = $props();\n</script>\n\n<!-- result will be <button>click me</button> -->\n<button>{@render children()}</button>\n```\n\n> [!NOTE] Note that you cannot have a prop called `children` if you also have content inside the component — for this reason, you should avoid having props with that name\n\n### Optional snippet props\n\nYou can declare snippet props as being optional. You can either use optional chaining to not render anything if the snippet isn't set...\n\n```svelte\n<script>\n let { children } = $props();\n</script>\n\n{@render children?.()}\n```\n\n...or use an `#if` block to render fallback content:\n\n```svelte\n<script>\n let { children } = $props();\n</script>\n\n{#if children}\n {@render children()}\n{:else}\n fallback content\n{/if}\n```\n\n## Typing snippets\n\nSnippets implement the `Snippet` interface imported from `'svelte'`:\n\n```svelte\n<script lang=\"ts\">\n\timport type { Snippet } from 'svelte';\n\n\tinterface Props {\n\t\tdata: any[];\n\t\tchildren: Snippet;\n\t\trow: Snippet<[any]>;\n\t}\n\n\tlet { data, children, row }: Props = $props();\n</script>\n```\n\nWith this change, red squigglies will appear if you try and use the component without providing a `data` prop and a `row` snippet. Notice that the type argument provided to `Snippet` is a tuple, since snippets can have multiple parameters.\n\nWe can tighten things up further by declaring a generic, so that `data` and `row` refer to the same type:\n\n```svelte\n<script lang=\"ts\" generics=\"T\">\n\timport type { Snippet } from 'svelte';\n\n\tlet {\n\t\tdata,\n\t\tchildren,\n\t\trow\n\t}: {\n\t\tdata: T[];\n\t\tchildren: Snippet;\n\t\trow: Snippet<[T]>;\n\t} = $props();\n</script>\n```\n\n## Exporting snippets\n\nSnippets declared at the top level of a `.svelte` file can be exported from a `<script module>` for use in other components, provided they don't reference any declarations in a non-module `<script>` (whether directly or indirectly, via other snippets) ([demo](/playground/untitled#H4sIAAAAAAAAE3WPwY7CMAxEf8UyB1hRgdhjl13Bga8gHFJipEqtGyUGFUX5dxJUtEB3b9bYM_MckHVLWOKut50TMuC5tpbEY4GnuiGP5T6gXG0-ykLSB8vW2oW_UCNZq7Snv_Rjx0Kc4kpc-6OrrfwoVlK3uQ4CaGMgwsl1LUwXy0f54J9-KV4vf20cNo7YkMu22aqAz4-oOLUI9YKluDPF4h_at-hX5PFyzA1tZ84N3fGpf8YfUU6GvDumLqDKmEqCjjCHUEX4hqDTWCU5PJ6Or38c4g1cPu9tnAEAAA==)):\n\n```svelte\n<script module>\n\texport { add };\n</script>\n\n{#snippet add(a, b)}\n\t{a} + {b} = {a + b}\n{/snippet}\n```\n\n> [!NOTE]\n> This requires Svelte 5.5.0 or newer\n\n## Programmatic snippets\n\nSnippets can be created programmatically with the [`createRawSnippet`](svelte#createRawSnippet) API. This is intended for advanced use cases.\n\n## Snippets and slots\n\nIn Svelte 4, content can be passed to components using [slots](legacy-slots). Snippets are more powerful and flexible, and so slots have been deprecated in Svelte 5."
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const books = [
{ title: "The Lord of the Rings" },
{ title: "To Kill a Mockingbird" },
{ title: "1984" }