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Merge pull request #430 from reactjs/sync-a8790ca8
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neighborhood999 authored Nov 20, 2023
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6 changes: 3 additions & 3 deletions src/components/Layout/getRouteMeta.tsx
Original file line number Diff line number Diff line change
Expand Up @@ -58,13 +58,13 @@ export interface RouteMeta {
order?: number;
}

type TravesalContext = RouteMeta & {
type TraversalContext = RouteMeta & {
currentIndex: number;
};

export function getRouteMeta(cleanedPath: string, routeTree: RouteItem) {
const breadcrumbs = getBreadcrumbs(cleanedPath, routeTree);
const ctx: TravesalContext = {
const ctx: TraversalContext = {
currentIndex: 0,
};
buildRouteMeta(cleanedPath, routeTree, ctx);
Expand All @@ -79,7 +79,7 @@ export function getRouteMeta(cleanedPath: string, routeTree: RouteItem) {
function buildRouteMeta(
searchPath: string,
currentRoute: RouteItem,
ctx: TravesalContext
ctx: TraversalContext
) {
ctx.currentIndex++;

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Expand Up @@ -74,7 +74,7 @@ Making plain JavaScript in React components reactive requires a compiler with a

## Offscreen Rendering {/*offscreen-rendering*/}

Offscreen rendering is an upcoming capability in React for rendering screens in the background without additional performance overhead. You can think of it as a version of the [`content-visiblity` CSS property](https://developer.mozilla.org/en-US/docs/Web/CSS/content-visibility) that works not only for DOM elements but React components, too. During our research, we've discovered a variety of use cases:
Offscreen rendering is an upcoming capability in React for rendering screens in the background without additional performance overhead. You can think of it as a version of the [`content-visibility` CSS property](https://developer.mozilla.org/en-US/docs/Web/CSS/content-visibility) that works not only for DOM elements but React components, too. During our research, we've discovered a variety of use cases:

- A router can prerender screens in the background so that when a user navigates to them, they're instantly available.
- A tab switching component can preserve the state of hidden tabs, so the user can switch between them without losing their progress.
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4 changes: 2 additions & 2 deletions src/content/learn/passing-data-deeply-with-context.md
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Expand Up @@ -985,7 +985,7 @@ export const places = [{
}, {
id: 5,
name: 'Chefchaouen, Marocco',
description: 'There are a few theories on why the houses are painted blue, including that the color repells mosquitos or that it symbolizes sky and heaven.',
description: 'There are a few theories on why the houses are painted blue, including that the color repels mosquitos or that it symbolizes sky and heaven.',
imageId: 'rTqKo46'
}, {
id: 6,
Expand Down Expand Up @@ -1124,7 +1124,7 @@ export const places = [{
}, {
id: 5,
name: 'Chefchaouen, Marocco',
description: 'There are a few theories on why the houses are painted blue, including that the color repells mosquitos or that it symbolizes sky and heaven.',
description: 'There are a few theories on why the houses are painted blue, including that the color repels mosquitos or that it symbolizes sky and heaven.',
imageId: 'rTqKo46'
}, {
id: 6,
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2 changes: 1 addition & 1 deletion src/content/reference/react-dom/components/form.md
Original file line number Diff line number Diff line change
Expand Up @@ -273,7 +273,7 @@ export async function deliverMessage(message) {

</Sandpack>

[//]: # 'Uncomment the next line, and delete this line after the `useOptimisitc` reference documentatino page is published'
[//]: # 'Uncomment the next line, and delete this line after the `useOptimistic` reference documentatino page is published'
[//]: # 'To learn more about the `useOptimistic` Hook see the [reference documentation](/reference/react/hooks/useOptimistic).'

### Handling form submission errors {/*handling-form-submission-errors*/}
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2 changes: 1 addition & 1 deletion src/content/reference/react/Component.md
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Expand Up @@ -632,7 +632,7 @@ class Form extends Component {
return (
<>
<input value={this.state.name} onChange={this.handleNameChange} />
<p>Hello, {this.state.name}.
<p>Hello, {this.state.name}.</p>
</>
);
}
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2 changes: 1 addition & 1 deletion src/content/reference/react/cache.md
Original file line number Diff line number Diff line change
Expand Up @@ -309,7 +309,7 @@ async function DemoProfile() {
React only provides cache access to the memoized function in a component. When calling <CodeStep step={1}>`getUser`</CodeStep> outside of a component, it will still evaluate the function but not read or update the cache.
This is because cache access is provided through a [context](/learn/passing-data-deeply-with-context) which is only accessibile from a component.
This is because cache access is provided through a [context](/learn/passing-data-deeply-with-context) which is only accessible from a component.
</Pitfall>
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2 changes: 1 addition & 1 deletion src/content/reference/react/directives.md
Original file line number Diff line number Diff line change
Expand Up @@ -19,5 +19,5 @@ Directives provide instructions to [bundlers compatible with React Server Compon

## Source code directives {/*source-code-directives*/}

* [`'use client'`](/reference/react/use-client) marks source files whose components execute on the client.
* [`'use client'`](/reference/react/use-client) lets you mark what code runs on the client.
* [`'use server'`](/reference/react/use-server) marks server-side functions that can be called from client-side code.
Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@ In this example, the constant `password` is tainted. Then `password` is used to

Other similar ways of deriving new values from tainted values like concatenating it into a larger string, converting it to base64, or returning a substring create untained values.

Tainting only protects against simple mistakes like explictly passing secret values to the client. Mistakes in calling the `taintUniqueValue` like using a global store outside of React, without the corresponding lifetime object, can cause the tainted value to become untainted. Tainting is a layer of protection; a secure app will have multiple layers of protection, well designed APIs, and isolation patterns.
Tainting only protects against simple mistakes like explicitly passing secret values to the client. Mistakes in calling the `taintUniqueValue` like using a global store outside of React, without the corresponding lifetime object, can cause the tainted value to become untainted. Tainting is a layer of protection; a secure app will have multiple layers of protection, well designed APIs, and isolation patterns.

</Pitfall>

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139 changes: 139 additions & 0 deletions src/content/reference/react/hooks.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,139 @@
---
title: "Built-in React Hooks"
---

<Intro>

*Hooks* let you use different React features from your components. You can either use the built-in Hooks or combine them to build your own. This page lists all built-in Hooks in React.

</Intro>

---

## State Hooks {/*state-hooks*/}

*State* lets a component ["remember" information like user input.](/learn/state-a-components-memory) For example, a form component can use state to store the input value, while an image gallery component can use state to store the selected image index.

To add state to a component, use one of these Hooks:

* [`useState`](/reference/react/useState) declares a state variable that you can update directly.
* [`useReducer`](/reference/react/useReducer) declares a state variable with the update logic inside a [reducer function.](/learn/extracting-state-logic-into-a-reducer)

```js
function ImageGallery() {
const [index, setIndex] = useState(0);
// ...
```
---
## Context Hooks {/*context-hooks*/}
*Context* lets a component [receive information from distant parents without passing it as props.](/learn/passing-props-to-a-component) For example, your app's top-level component can pass the current UI theme to all components below, no matter how deep.
* [`useContext`](/reference/react/useContext) reads and subscribes to a context.
```js
function Button() {
const theme = useContext(ThemeContext);
// ...
```
---
## Ref Hooks {/*ref-hooks*/}
*Refs* let a component [hold some information that isn't used for rendering,](/learn/referencing-values-with-refs) like a DOM node or a timeout ID. Unlike with state, updating a ref does not re-render your component. Refs are an "escape hatch" from the React paradigm. They are useful when you need to work with non-React systems, such as the built-in browser APIs.
* [`useRef`](/reference/react/useRef) declares a ref. You can hold any value in it, but most often it's used to hold a DOM node.
* [`useImperativeHandle`](/reference/react/useImperativeHandle) lets you customize the ref exposed by your component. This is rarely used.
```js
function Form() {
const inputRef = useRef(null);
// ...
```
---
## Effect Hooks {/*effect-hooks*/}
*Effects* let a component [connect to and synchronize with external systems.](/learn/synchronizing-with-effects) This includes dealing with network, browser DOM, animations, widgets written using a different UI library, and other non-React code.
* [`useEffect`](/reference/react/useEffect) connects a component to an external system.
```js
function ChatRoom({ roomId }) {
useEffect(() => {
const connection = createConnection(roomId);
connection.connect();
return () => connection.disconnect();
}, [roomId]);
// ...
```
Effects are an "escape hatch" from the React paradigm. Don't use Effects to orchestrate the data flow of your application. If you're not interacting with an external system, [you might not need an Effect.](/learn/you-might-not-need-an-effect)
There are two rarely used variations of `useEffect` with differences in timing:
* [`useLayoutEffect`](/reference/react/useLayoutEffect) fires before the browser repaints the screen. You can measure layout here.
* [`useInsertionEffect`](/reference/react/useInsertionEffect) fires before React makes changes to the DOM. Libraries can insert dynamic CSS here.
---
## Performance Hooks {/*performance-hooks*/}
A common way to optimize re-rendering performance is to skip unnecessary work. For example, you can tell React to reuse a cached calculation or to skip a re-render if the data has not changed since the previous render.
To skip calculations and unnecessary re-rendering, use one of these Hooks:
- [`useMemo`](/reference/react/useMemo) lets you cache the result of an expensive calculation.
- [`useCallback`](/reference/react/useCallback) lets you cache a function definition before passing it down to an optimized component.
```js
function TodoList({ todos, tab, theme }) {
const visibleTodos = useMemo(() => filterTodos(todos, tab), [todos, tab]);
// ...
}
```
Sometimes, you can't skip re-rendering because the screen actually needs to update. In that case, you can improve performance by separating blocking updates that must be synchronous (like typing into an input) from non-blocking updates which don't need to block the user interface (like updating a chart).
To prioritize rendering, use one of these Hooks:
- [`useTransition`](/reference/react/useTransition) lets you mark a state transition as non-blocking and allow other updates to interrupt it.
- [`useDeferredValue`](/reference/react/useDeferredValue) lets you defer updating a non-critical part of the UI and let other parts update first.
---
## Resource Hooks {/*resource-hooks*/}
*Resources* can be accessed by a component without having them as part of their state. For example, a component can read a message from a Promise or read styling information from a context.
To read a value from a resource, use this Hook:
- [`use`](/reference/react/use) lets you read the value of a resource like a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) or [context](/learn/passing-data-deeply-with-context).
```js
function MessageComponent({ messagePromise }) {
const message = use(messagePromise);
const theme = use(ThemeContext);
// ...
}
```
---
## Other Hooks {/*other-hooks*/}
These Hooks are mostly useful to library authors and aren't commonly used in the application code.
- [`useDebugValue`](/reference/react/useDebugValue) lets you customize the label React DevTools displays for your custom Hook.
- [`useId`](/reference/react/useId) lets a component associate a unique ID with itself. Typically used with accessibility APIs.
- [`useSyncExternalStore`](/reference/react/useSyncExternalStore) lets a component subscribe to an external store.
---
## Your own Hooks {/*your-own-hooks*/}
You can also [define your own custom Hooks](/learn/reusing-logic-with-custom-hooks#extracting-your-own-custom-hook-from-a-component) as JavaScript functions.
149 changes: 20 additions & 129 deletions src/content/reference/react/index.md
Original file line number Diff line number Diff line change
@@ -1,139 +1,30 @@
---
title: "Built-in React Hooks"
title: React Reference Overview
---

<Intro>

*Hooks* let you use different React features from your components. You can either use the built-in Hooks or combine them to build your own. This page lists all built-in Hooks in React.

This section provides detailed reference documentation for working with React.
For an introduction to React, please visit the [Learn](/learn) section.
</Intro>

---

## State Hooks {/*state-hooks*/}

*State* lets a component ["remember" information like user input.](/learn/state-a-components-memory) For example, a form component can use state to store the input value, while an image gallery component can use state to store the selected image index.

To add state to a component, use one of these Hooks:

* [`useState`](/reference/react/useState) declares a state variable that you can update directly.
* [`useReducer`](/reference/react/useReducer) declares a state variable with the update logic inside a [reducer function.](/learn/extracting-state-logic-into-a-reducer)

```js
function ImageGallery() {
const [index, setIndex] = useState(0);
// ...
```
---
## Context Hooks {/*context-hooks*/}
*Context* lets a component [receive information from distant parents without passing it as props.](/learn/passing-props-to-a-component) For example, your app's top-level component can pass the current UI theme to all components below, no matter how deep.
* [`useContext`](/reference/react/useContext) reads and subscribes to a context.
```js
function Button() {
const theme = useContext(ThemeContext);
// ...
```
---
## Ref Hooks {/*ref-hooks*/}
*Refs* let a component [hold some information that isn't used for rendering,](/learn/referencing-values-with-refs) like a DOM node or a timeout ID. Unlike with state, updating a ref does not re-render your component. Refs are an "escape hatch" from the React paradigm. They are useful when you need to work with non-React systems, such as the built-in browser APIs.
* [`useRef`](/reference/react/useRef) declares a ref. You can hold any value in it, but most often it's used to hold a DOM node.
* [`useImperativeHandle`](/reference/react/useImperativeHandle) lets you customize the ref exposed by your component. This is rarely used.
```js
function Form() {
const inputRef = useRef(null);
// ...
```
---
## Effect Hooks {/*effect-hooks*/}
*Effects* let a component [connect to and synchronize with external systems.](/learn/synchronizing-with-effects) This includes dealing with network, browser DOM, animations, widgets written using a different UI library, and other non-React code.
* [`useEffect`](/reference/react/useEffect) connects a component to an external system.
```js
function ChatRoom({ roomId }) {
useEffect(() => {
const connection = createConnection(roomId);
connection.connect();
return () => connection.disconnect();
}, [roomId]);
// ...
```
Our The React reference documentation is broken down into functional subsections:

Effects are an "escape hatch" from the React paradigm. Don't use Effects to orchestrate the data flow of your application. If you're not interacting with an external system, [you might not need an Effect.](/learn/you-might-not-need-an-effect)
## React {/*react*/}
Programmatic React features:
* [Hooks](/reference/react/hooks) - Use different React features from your components.
* [Components](/reference/react/components) - Documents built-in components that you can use in your JSX.
* [APIs](/reference/react/apis) - APIs that are useful for defining components.
* [Directives](/reference/react/directives) - Provide instructions to bundlers compatible with React Server Components.

There are two rarely used variations of `useEffect` with differences in timing:
* [`useLayoutEffect`](/reference/react/useLayoutEffect) fires before the browser repaints the screen. You can measure layout here.
* [`useInsertionEffect`](/reference/react/useInsertionEffect) fires before React makes changes to the DOM. Libraries can insert dynamic CSS here.
---
## Performance Hooks {/*performance-hooks*/}
A common way to optimize re-rendering performance is to skip unnecessary work. For example, you can tell React to reuse a cached calculation or to skip a re-render if the data has not changed since the previous render.
To skip calculations and unnecessary re-rendering, use one of these Hooks:
- [`useMemo`](/reference/react/useMemo) lets you cache the result of an expensive calculation.
- [`useCallback`](/reference/react/useCallback) lets you cache a function definition before passing it down to an optimized component.
```js
function TodoList({ todos, tab, theme }) {
const visibleTodos = useMemo(() => filterTodos(todos, tab), [todos, tab]);
// ...
}
```
Sometimes, you can't skip re-rendering because the screen actually needs to update. In that case, you can improve performance by separating blocking updates that must be synchronous (like typing into an input) from non-blocking updates which don't need to block the user interface (like updating a chart).
To prioritize rendering, use one of these Hooks:
- [`useTransition`](/reference/react/useTransition) lets you mark a state transition as non-blocking and allow other updates to interrupt it.
- [`useDeferredValue`](/reference/react/useDeferredValue) lets you defer updating a non-critical part of the UI and let other parts update first.
---
## Resource Hooks {/*resource-hooks*/}
*Resources* can be accessed by a component without having them as part of their state. For example, a component can read a message from a Promise or read styling information from a context.
To read a value from a resource, use this Hook:
- [`use`](/reference/react/use) lets you read the value of a resource like a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) or [context](/learn/passing-data-deeply-with-context).
```js
function MessageComponent({ messagePromise }) {
const message = use(messagePromise);
const theme = use(ThemeContext);
// ...
}
```
---
## Other Hooks {/*other-hooks*/}
These Hooks are mostly useful to library authors and aren't commonly used in the application code.
- [`useDebugValue`](/reference/react/useDebugValue) lets you customize the label React DevTools displays for your custom Hook.
- [`useId`](/reference/react/useId) lets a component associate a unique ID with itself. Typically used with accessibility APIs.
- [`useSyncExternalStore`](/reference/react/useSyncExternalStore) lets a component subscribe to an external store.
---
## React DOM {/*react-dom*/}
React-dom contains features that are only supported for web applications
(which run in the browser DOM environment). This section is broken into the following:

## Your own Hooks {/*your-own-hooks*/}
* [Hooks](/reference/react-dom/hooks) - Hooks for web applications which run in the browser DOM environment.
* [Components](/reference/react-dom/components) - React supports all of the browser built-in HTML and SVG components.
* [APIs](/reference/react-dom) - The `react-dom` package contains methods supported only in web applications.
* [Client APIs](/reference/react-dom/client) - The `react-dom/client` APIs let you render React components on the client (in the browser).
* [Server APIs](/reference/react-dom/server) - The `react-dom/server` APIs let you render React components to HTML on the server.

You can also [define your own custom Hooks](/learn/reusing-logic-with-custom-hooks#extracting-your-own-custom-hook-from-a-component) as JavaScript functions.
## Legacy APIs {/*legacy-apis*/}
* [Legacy APIs](/reference/react/legacy) - Exported from the react package, but not recommended for use in newly written code.
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