diff --git a/src/content/reference/react/useEffectEvent.md b/src/content/reference/react/useEffectEvent.md
index bfac4c48e89..50248c85a9b 100644
--- a/src/content/reference/react/useEffectEvent.md
+++ b/src/content/reference/react/useEffectEvent.md
@@ -4,91 +4,551 @@ title: useEffectEvent
-`useEffectEvent` is a React Hook that lets you extract non-reactive logic from your Effects into a reusable function called an [Effect Event](/learn/separating-events-from-effects#declaring-an-effect-event).
+`useEffectEvent` is a React Hook that lets you separate events from Effects.
```js
-const onSomething = useEffectEvent(callback)
+const onEvent = useEffectEvent(callback)
```
+---
+
## Reference {/*reference*/}
### `useEffectEvent(callback)` {/*useeffectevent*/}
-Call `useEffectEvent` at the top level of your component to declare an Effect Event. Effect Events are functions you can call inside Effects, such as `useEffect`:
+Call `useEffectEvent` at the top level of your component to declare an Effect Event.
-```js {4-6,11}
+```js {4,6}
import { useEffectEvent, useEffect } from 'react';
function ChatRoom({ roomId, theme }) {
const onConnected = useEffectEvent(() => {
showNotification('Connected!', theme);
});
+}
+```
+
+Effect Events are functions you can call inside Effects, such as `useEffect`.
+
+[See more examples below.](#usage)
+
+#### Parameters {/*parameters*/}
+
+* `callback`: A function containing the logic for your Effect Event. The function can accept any number of arguments and return any value. When you call the returned Effect Event function, the `callback` always accesses the latest values from props and state at the time of the call.
+
+#### Returns {/*returns*/}
+
+`useEffectEvent` returns an Effect Event function with the same type signature as your `callback`.
+
+You can call this function inside `useEffect`, `useLayoutEffect`, `useInsertionEffect`, or from within other Effect Events in the same component.
+
+#### Caveats {/*caveats*/}
+
+* `useEffectEvent` is a Hook, so you can only call it **at the top level of your component** or your own Hooks. You can't call it inside loops or conditions. If you need that, extract a new component and move the Effect Event into it.
+* Effect Events can only be called from inside Effects or other Effect Events. Do not call them during rendering or pass them to other components or Hooks. The [`eslint-plugin-react-hooks`](/reference/eslint-plugin-react-hooks) linter enforces this restriction.
+* Do not use `useEffectEvent` to avoid specifying dependencies in your Effect's dependency array. This hides bugs and makes your code harder to understand. Only use it for logic that is genuinely an event fired from Effects.
+* Effect Event functions do not have a stable identity. Their identity intentionally changes on every render.
+
+
+
+#### Why are Effect Events not stable? {/*why-are-effect-events-not-stable*/}
+
+Unlike `set` functions from `useState` or refs, Effect Event functions do not have a stable identity. Their identity intentionally changes on every render:
+
+```js
+// 🔴 Wrong: including Effect Event in dependencies
+useEffect(() => {
+ onSomething();
+}, [onSomething]); // ESLint will warn about this
+```
+
+This is a deliberate design choice. Effect Events are meant to be called only from within Effects in the same component. Since you can only call them locally and cannot pass them to other components or include them in dependency arrays, a stable identity would serve no purpose, and would actually mask bugs.
+
+The non-stable identity acts as a runtime assertion: if your code incorrectly depends on the function identity, you'll see the Effect re-running on every render, making the bug obvious.
+
+This design reinforces the rule that Effect Events are "escape hatches" for reading the latest values, not general purpose callbacks to be passed around.
+
+
+
+---
+
+## Usage {/*usage*/}
+
+
+### Using an event in an Effect {/*using-an-event-in-an-effect*/}
+
+Call `useEffectEvent` at the top level of your component to create an *Effect Event*:
+
+
+```js [[1, 1, "onConnected"]]
+const onConnected = useEffectEvent(() => {
+ if (!muted) {
+ showNotification('Connected!');
+ }
+});
+```
+
+`useEffectEvent` accepts an `event callback` and returns an Effect Event. The Effect Event is a function that can be called inside of Effects without re-connecting the Effect:
+
+```js [[1, 3, "onConnected"]]
+useEffect(() => {
+ const connection = createConnection(roomId);
+ connection.on('connected', onConnected);
+ connection.connect();
+ return () => {
+ connection.disconnect();
+ }
+}, [roomId]);
+```
+
+Since `onConnected` is an Effect Event, `muted` and `onConnect` are not in the Effect dependencies.
+
+
+
+##### Don't use Effect Events to skip dependencies {/*pitfall-skip-dependencies*/}
+
+It might be tempting to use `useEffectEvent` to avoid listing dependencies that you think are "unnecessary." However, this hides bugs and makes your code harder to understand:
+
+```js
+// 🔴 Wrong: Using Effect Events to hide dependencies
+const logVisit = useEffectEvent(() => {
+ log(pageUrl);
+});
+
+useEffect(() => {
+ logVisit()
+}, []); // Missing pageUrl means you miss logs
+```
+
+If a value should cause your Effect to re-run, keep it as a dependency. Only use Effect Events for logic that genuinely should not re-trigger your Effect.
+
+See [Separating Events from Effects](/learn/separating-events-from-effects) to learn more.
+
+
+
+---
+
+### Using a timer with latest values {/*using-a-timer-with-latest-values*/}
+
+When you use `setInterval` or `setTimeout` in an Effect, you often want to read the latest state values without restarting the timer whenever those values change.
+
+This counter increments by the current `increment` value every second. The `onTick` Effect Event reads the latest `increment` without causing the interval to restart:
+
+
+
+```js
+import { useState, useEffect, useEffectEvent } from 'react';
+
+export default function Timer() {
+ const [count, setCount] = useState(0);
+ const [increment, setIncrement] = useState(1);
+
+ const onTick = useEffectEvent(() => {
+ setCount(c => c + increment);
+ });
+
+ useEffect(() => {
+ const id = setInterval(() => {
+ onTick();
+ }, 1000);
+ return () => {
+ clearInterval(id);
+ };
+ }, []);
+
+ return (
+ <>
+
+ Counter: {count}
+
+
+
+
+ Every second, increment by:
+
+ {increment}
+
+
+ >
+ );
+}
+```
+
+```css
+button { margin: 10px; }
+```
+
+
+
+Try changing the increment value while the timer is running. The counter immediately uses the new increment value, but the timer keeps ticking smoothly without restarting.
+
+---
+
+### Using an event listener with latest state {/*using-an-event-listener-with-latest-state*/}
+
+When you set up an event listener in an Effect, you often need to read the latest state in the callback. Without `useEffectEvent`, you would need to include the state in your dependencies, causing the listener to be removed and re-added on every change.
+
+This example shows a dot that follows the cursor, but only when "Can move" is checked. The `onMove` Effect Event always reads the latest `canMove` value without re-running the Effect:
+
+
+
+```js
+import { useState, useEffect, useEffectEvent } from 'react';
+
+export default function App() {
+ const [position, setPosition] = useState({ x: 0, y: 0 });
+ const [canMove, setCanMove] = useState(true);
+
+ const onMove = useEffectEvent(e => {
+ if (canMove) {
+ setPosition({ x: e.clientX, y: e.clientY });
+ }
+ });
useEffect(() => {
- const connection = createConnection(serverUrl, roomId);
+ window.addEventListener('pointermove', onMove);
+ return () => window.removeEventListener('pointermove', onMove);
+ }, []);
+
+ return (
+ <>
+
+
+
+ >
+ );
+}
+```
+
+```css
+body {
+ height: 200px;
+}
+```
+
+
+
+Toggle the checkbox and move your cursor. The dot responds immediately to the checkbox state, but the event listener is only set up once when the component mounts.
+
+---
+
+### Avoid reconnecting to external systems {/*showing-a-notification-without-reconnecting*/}
+
+A common use case for `useEffectEvent` is when you want to do something in response to an Effect, but that "something" depends on a value you don't want to react to.
+
+In this example, a chat component connects to a room and shows a notification when connected. The user can mute notifications with a checkbox. However, you don't want to reconnect to the chat room every time the user changes the settings:
+
+
+
+```json package.json hidden
+{
+ "dependencies": {
+ "react": "latest",
+ "react-dom": "latest",
+ "react-scripts": "latest",
+ "toastify-js": "1.12.0"
+ },
+ "scripts": {
+ "start": "react-scripts start",
+ "build": "react-scripts build",
+ "test": "react-scripts test --env=jsdom",
+ "eject": "react-scripts eject"
+ }
+}
+```
+
+```js
+import { useState, useEffect, useEffectEvent } from 'react';
+import { createConnection } from './chat.js';
+import { showNotification } from './notifications.js';
+
+function ChatRoom({ roomId, muted }) {
+ const onConnected = useEffectEvent((roomId) => {
+ console.log('✅ Connected to ' + roomId + ' (muted: ' + muted + ')');
+ if (!muted) {
+ showNotification('Connected to ' + roomId);
+ }
+ });
+
+ useEffect(() => {
+ const connection = createConnection(roomId);
+ console.log('⏳ Connecting to ' + roomId + '...');
connection.on('connected', () => {
- onConnected();
+ onConnected(roomId);
});
connection.connect();
- return () => connection.disconnect();
+ return () => {
+ console.log('❌ Disconnected from ' + roomId);
+ connection.disconnect();
+ }
}, [roomId]);
- // ...
+ return
Welcome to the {roomId} room!
;
+}
+
+export default function App() {
+ const [roomId, setRoomId] = useState('general');
+ const [muted, setMuted] = useState(false);
+ return (
+ <>
+
+
+
+
+ >
+ );
}
```
-[See more examples below.](#usage)
+```js src/chat.js
+const serverUrl = 'https://localhost:1234';
+
+export function createConnection(roomId) {
+ // A real implementation would actually connect to the server
+ let connectedCallback;
+ let timeout;
+ return {
+ connect() {
+ timeout = setTimeout(() => {
+ if (connectedCallback) {
+ connectedCallback();
+ }
+ }, 100);
+ },
+ on(event, callback) {
+ if (connectedCallback) {
+ throw Error('Cannot add the handler twice.');
+ }
+ if (event !== 'connected') {
+ throw Error('Only "connected" event is supported.');
+ }
+ connectedCallback = callback;
+ },
+ disconnect() {
+ clearTimeout(timeout);
+ }
+ };
+}
+```
-#### Parameters {/*parameters*/}
+```js src/notifications.js
+import Toastify from 'toastify-js';
+import 'toastify-js/src/toastify.css';
+
+export function showNotification(message, theme) {
+ Toastify({
+ text: message,
+ duration: 2000,
+ gravity: 'top',
+ position: 'right',
+ style: {
+ background: theme === 'dark' ? 'black' : 'white',
+ color: theme === 'dark' ? 'white' : 'black',
+ },
+ }).showToast();
+}
+```
-- `callback`: A function containing the logic for your Effect Event. When you define an Effect Event with `useEffectEvent`, the `callback` always accesses the latest values from props and state when it is invoked. This helps avoid issues with stale closures.
+```css
+label { display: block; margin-top: 10px; }
+```
-#### Returns {/*returns*/}
+
-Returns an Effect Event function. You can call this function inside `useEffect`, `useLayoutEffect`, or `useInsertionEffect`.
+Try switching rooms. The chat reconnects and shows a notification. Now mute the notifications. Since `muted` is read inside the Effect Event rather than the Effect, the chat stays connected.
-#### Caveats {/*caveats*/}
+---
-- **Only call inside Effects:** Effect Events should only be called within Effects. Define them just before the Effect that uses them. Do not pass them to other components or hooks. The [`eslint-plugin-react-hooks`](/reference/eslint-plugin-react-hooks) linter (version 6.1.1 or higher) will enforce this restriction to prevent calling Effect Events in the wrong context.
-- **Not a dependency shortcut:** Do not use `useEffectEvent` to avoid specifying dependencies in your Effect's dependency array. This can hide bugs and make your code harder to understand. Prefer explicit dependencies or use refs to compare previous values if needed.
-- **Use for non-reactive logic:** Only use `useEffectEvent` to extract logic that does not depend on changing values.
+### Using Effect Events in custom Hooks {/*using-effect-events-in-custom-hooks*/}
-___
+You can use `useEffectEvent` inside your own custom Hooks. This lets you create reusable Hooks that encapsulate Effects while keeping some values non-reactive:
-## Usage {/*usage*/}
+
-### Reading the latest props and state {/*reading-the-latest-props-and-state*/}
+```js
+import { useState, useEffect, useEffectEvent } from 'react';
-Typically, when you access a reactive value inside an Effect, you must include it in the dependency array. This makes sure your Effect runs again whenever that value changes, which is usually the desired behavior.
+function useInterval(callback, delay) {
+ const onTick = useEffectEvent(callback);
-But in some cases, you may want to read the most recent props or state inside an Effect without causing the Effect to re-run when those values change.
+ useEffect(() => {
+ if (delay === null) {
+ return;
+ }
+ const id = setInterval(() => {
+ onTick();
+ }, delay);
+ return () => clearInterval(id);
+ }, [delay]);
+}
+
+function Counter({ incrementBy }) {
+ const [count, setCount] = useState(0);
+
+ useInterval(() => {
+ setCount(c => c + incrementBy);
+ }, 1000);
+
+ return (
+
+
Count: {count}
+
Incrementing by {incrementBy} every second
+
+ );
+}
-To [read the latest props or state](/learn/separating-events-from-effects#reading-latest-props-and-state-with-effect-events) in your Effect, without making those values reactive, include them in an Effect Event.
+export default function App() {
+ const [incrementBy, setIncrementBy] = useState(1);
+
+ return (
+ <>
+
+
+
+ >
+ );
+}
+```
-```js {7-9,12}
-import { useEffect, useContext, useEffectEvent } from 'react';
+```css
+label { display: block; margin-bottom: 8px; }
+```
-function Page({ url }) {
- const { items } = useContext(ShoppingCartContext);
- const numberOfItems = items.length;
+
- const onNavigate = useEffectEvent((visitedUrl) => {
- logVisit(visitedUrl, numberOfItems);
+In this example, `useInterval` is a custom Hook that sets up an interval. The `callback` passed to it is wrapped in an Effect Event, so the interval does not reset even if a new `callback` is passed in every render.
+
+---
+
+## Troubleshooting {/*troubleshooting*/}
+
+### I'm getting an error: "A function wrapped in useEffectEvent can't be called during rendering" {/*cant-call-during-rendering*/}
+
+This error means you're calling an Effect Event function during the render phase of your component. Effect Events can only be called from inside Effects or other Effect Events.
+
+```js
+function MyComponent({ data }) {
+ const onLog = useEffectEvent(() => {
+ console.log(data);
});
+ // 🔴 Wrong: calling during render
+ onLog();
+
+ // ✅ Correct: call from an Effect
useEffect(() => {
- onNavigate(url);
- }, [url]);
+ onLog();
+ }, []);
- // ...
+ return
{data}
;
}
```
-In this example, the Effect should re-run after a render when `url` changes (to log the new page visit), but it should **not** re-run when `numberOfItems` changes. By wrapping the logging logic in an Effect Event, `numberOfItems` becomes non-reactive. It's always read from the latest value without triggering the Effect.
+If you need to run logic during render, don't wrap it in `useEffectEvent`. Call the logic directly or move it into an Effect.
+
+---
+
+### I'm getting a lint error: "Functions returned from useEffectEvent must not be included in the dependency array" {/*effect-event-in-deps*/}
+
+If you see a warning like "Functions returned from `useEffectEvent` must not be included in the dependency array", remove the Effect Event from your dependencies:
+
+```js
+const onSomething = useEffectEvent(() => {
+ // ...
+});
+
+// 🔴 Wrong: Effect Event in dependencies
+useEffect(() => {
+ onSomething();
+}, [onSomething]);
+
+// ✅ Correct: no Effect Event in dependencies
+useEffect(() => {
+ onSomething();
+}, []);
+```
+
+Effect Events are designed to be called from Effects without being listed as dependencies. The linter enforces this because the function identity is [intentionally not stable](#why-are-effect-events-not-stable). Including it would cause your Effect to re-run on every render.
-You can pass reactive values like `url` as arguments to the Effect Event to keep them reactive while accessing the latest non-reactive values inside the event.
+---
+
+### I'm getting a lint error: "... is a function created with useEffectEvent, and can only be called from Effects" {/*effect-event-called-outside-effect*/}
+
+If you see a warning like "... is a function created with React Hook `useEffectEvent`, and can only be called from Effects and Effect Events", you're calling the function from the wrong place:
+
+```js
+const onSomething = useEffectEvent(() => {
+ console.log(value);
+});
+
+// 🔴 Wrong: calling from event handler
+function handleClick() {
+ onSomething();
+}
+
+// 🔴 Wrong: passing to child component
+return ;
+
+// ✅ Correct: calling from Effect
+useEffect(() => {
+ onSomething();
+}, []);
+```
+Effect Events are specifically designed to be used in Effects local to the component they're defined in. If you need a callback for event handlers or to pass to children, use a regular function or `useCallback` instead.
\ No newline at end of file