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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

Copy link
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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

Copy link
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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix"); } } catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

Copy link
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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms"); } } catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links"); } } catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); } })(); (function(){ try { var __m = "youtube.com"; var __re = new RegExp('^' + "youtube\\.com" + '
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default"); } } catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers"); } } catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode"); } } catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); } })(); })();
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122 changes: 121 additions & 1 deletion src/content/reference/react/Fragment.md
Original file line numberDiff line numberDiff line change
Expand Up@@ -4,7 +4,9 @@ title: <Fragment> (<>...</>)

<Intro>

`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.
`<Fragment>`, often used via `<>...</>` syntax, lets you group elements without a wrapper node.

<Experimental> Fragments can also accept refs, which enable interacting with underlying DOM nodes without adding wrapper elements. See reference and usage below.</Experimental>

```js
<>
Expand All@@ -28,13 +30,42 @@ Wrap elements in `<Fragment>` to group them together in situations where you nee
#### Props {/*props*/}

- **optional** `key`: Fragments declared with the explicit `<Fragment>` syntax may have [keys.](/learn/rendering-lists#keeping-list-items-in-order-with-key)
- <ExperimentalBadge /> **optional** `ref`: A ref object (e.g. from [`useRef`](/reference/react/useRef)) or [callback function](/reference/react-dom/components/common#ref-callback). React provides a `FragmentInstance` as the ref value that implements methods for interacting with the DOM nodes wrapped by the Fragment.

### <ExperimentalBadge /> FragmentInstance {/*fragmentinstance*/}

When you pass a ref to a fragment, React provides a `FragmentInstance` object with methods for interacting with the DOM nodes wrapped by the fragment:

**Event handling methods:**
- `addEventListener(type, listener, options?)`: Adds an event listener to all first-level DOM children of the Fragment.
- `removeEventListener(type, listener, options?)`: Removes an event listener from all first-level DOM children of the Fragment.
- `dispatchEvent(event)`: Dispatches an event to a virtual child of the Fragment to call any added listeners and can bubble to the DOM parent.

**Layout methods:**
- `compareDocumentPosition(otherNode)`: Compares the document position of the Fragment with another node.
- If the Fragment has children, the native `compareDocumentPosition` value is returned.
- Empty Fragments will attempt to compare positioning within the React tree and include `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- Elements that have a different relationship in the React tree and DOM tree due to portaling or other insertions are `Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC`.
- `getClientRects()`: Returns a flat array of `DOMRect` objects representing the bounding rectangles of all children.
- `getRootNode()`: Returns the root node containing the Fragment's parent DOM node.

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Dumb question but why can we easily get the root node, but not the parent node?

Wouldn't this be more flexible alternative to findDOMNode? fragmentRef.current.parent.getRootNode() ?


**Focus management methods:**
- `focus(options?)`: Focuses the first focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `focusLast(options?)`: Focuses the last focusable DOM node in the Fragment. Focus is attempted on nested children depth-first.
- `blur()`: Removes focus if `document.activeElement` is within the Fragment.

**Observer methods:**
- `observeUsing(observer)`: Starts observing the Fragment's DOM children with an IntersectionObserver or ResizeObserver.
- `unobserveUsing(observer)`: Stops observing the Fragment's DOM children with the specified observer.

#### Caveats {/*caveats*/}

- If you want to pass `key` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment key={yourKey}>...</Fragment>`.

- React does not [reset state](/learn/preserving-and-resetting-state) when you go from rendering `<><Child /></>` to `[<Child />]` or back, or when you go from rendering `<><Child /></>` to `<Child />` and back. This only works a single level deep: for example, going from `<><><Child /></></>` to `<Child />` resets the state. See the precise semantics [here.](https://gist.github.com/clemmy/b3ef00f9507909429d8aa0d3ee4f986b)

- <ExperimentalBadge /> If you want to pass `ref` to a Fragment, you can't use the `<>...</>` syntax. You have to explicitly import `Fragment` from `'react'` and render `<Fragment ref={yourRef}>...</Fragment>`.

---

## Usage {/*usage*/}
Expand DownExpand Up@@ -208,3 +239,92 @@ function PostBody({ body }) {
```

</Sandpack>

---

### <ExperimentalBadge /> Using Fragment refs for DOM interaction {/*using-fragment-refs-for-dom-interaction*/}

Fragment refs allow you to interact with the DOM nodes wrapped by a Fragment without adding extra wrapper elements. This is useful for event handling, visibility tracking, focus management, and replacing deprecated patterns like `ReactDOM.findDOMNode()`.

```js
import { Fragment } from 'react';

function ClickableFragment({ children, onClick }) {
return (
<Fragment ref={fragmentInstance => {
fragmentInstance.addEventListener('click', handleClick);
return () => fragmentInstance.removeEventListener('click', handleClick);
}}>
{children}
</Fragment>
);
}
```
---

### <ExperimentalBadge /> Tracking visibility with Fragment refs {/*tracking-visibility-with-fragment-refs*/}

Fragment refs are useful for visibility tracking and intersection observation. This enables you to monitor when content becomes visible without requiring the child Components to expose refs:

```js {19,21,31-34}
import { Fragment, useRef, useLayoutEffect } from 'react';

function VisibilityObserverFragment({ threshold = 0.5, onVisibilityChange, children }) {
const fragmentRef = useRef(null);

useLayoutEffect(() => {
const observer = new IntersectionObserver(
(entries) => {
onVisibilityChange(entries.some(entry => entry.isIntersecting))
},
{ threshold }
);

fragmentRef.current.observeUsing(observer);
return () => fragmentRef.current.unobserveUsing(observer);
}, [threshold, onVisibilityChange]);

return (
<Fragment ref={fragmentRef}>
{children}
</Fragment>
);
}

function MyComponent() {
const handleVisibilityChange = (isVisible) => {
console.log('Component is', isVisible ? 'visible' : 'hidden');
};

return (
<VisibilityObserverFragment onVisibilityChange={handleVisibilityChange}>
<SomeThirdPartyComponent />
<AnotherComponent />
</VisibilityObserverFragment>
);
}
```

This pattern is an alternative to Effect-based visibility logging, which is an anti-pattern in most cases. Relying on Effects alone does not guarantee that the rendered Component is observable by the user.

---

### <ExperimentalBadge /> Focus management with Fragment refs {/*focus-management-with-fragment-refs*/}

Fragment refs provide focus management methods that work across all DOM nodes within the Fragment:

```js
import { Fragment, useRef } from 'react';

function FocusFragment({ children }) {
const fragmentRef = useRef(null);

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looks like a typo, PR #8056


return (
<Fragment ref={(fragmentInstance) => fragmentInstance?.focus()}>
{children}
</Fragment>
);
}
```

The `focus()` method focuses the first focusable element within the Fragment, while `focusLast()` focuses the last focusable element.