React 是一个开源 JavaScript 库，用于构建出色且复杂的用户界面，并且是 JavaScript 生态系统中最受欢迎的库之一。
React hooks 是允许您在功能组件中使用 React 状态和其他功能的函数，从而无需编写复杂的 React 类即可实现处理副作用和访问上下文等任务。使用 React hooks 还可以增强开发人员的代码可读性和可维护性。
在本文中，我将分享 38 个 React.js 钩子及其用例的列表，这可以被认为是 React 和 JavaScript 开发人员的最佳资源之一。
管理本地组件状态。
import { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
return (
<div>
<button onClick={() => setCount(count + 1)}>Increment</button>
<p>Count: {count}</p>
</div>
);
}
在函数组件中执行副作用。
import { useEffect, useState } from 'react';
function DataFetcher() {
const [data, setData] = useState(null);
useEffect(() => {
fetch('https://api.example.com/data')
.then(response => response.json())
.then(data => setData(data));
}, []);
return <div>Data: {data ? JSON.stringify(data) : 'Loading...'}</div>;
}
使用组件中的上下文。
import { useContext } from 'react';
import { ThemeContext } from './ThemeContext';
function ThemedButton() {
const theme = useContext(ThemeContext);
return <button style={{ background: theme.background }}>Click me</button>;
}
管理复杂的状态逻辑
import { useReducer } from 'react';
const initialState = { count: 0 };
function reducer(state, action) {
switch (action.type) {
case 'increment':
return { count: state.count + 1 };
case 'decrement':
return { count: state.count - 1 };
default:
throw new Error();
}
}
function Counter() {
const [state, dispatch] = useReducer(reducer, initialState);
return (
<div>
<button onClick={() => dispatch({ type: 'decrement' })}>-</button>
<span>{state.count}</span>
<button onClick={() => dispatch({ type: 'increment' })}>+</button>
</div>
);
}
返回记忆的回调函数。
import { useCallback, useState } from 'react';
function CallbackComponent() {
const [count, setCount] = useState(0);
const increment = useCallback(() => {
setCount(count + 1);
}, [count]);
return <button onClick={increment}>Count: {count}</button>;
}
记忆昂贵的计算，即存储资源密集型计算的结果以供将来使用。
import { useMemo, useState } from 'react';
function Fibonacci() {
const [num, setNum] = useState(1);
const fib = useMemo(() => {
const computeFib = (n) => (n <= 1 ? n : computeFib(n - 1) + computeFib(n - 2));
return computeFib(num);
}, [num]);
return (
<div>
<button onClick={() => setNum(num + 1)}>Next Fibonacci</button>
<p>Fibonacci of {num} is {fib}</p>
</div>
);
}
访问 DOM 元素或存储可变值。
import { useRef } from 'react';
function TextInputWithFocusButton() {
const inputEl = useRef(null);
const onButtonClick = () => {
inputEl.current.focus();
};
return (
<div>
<input ref={inputEl} type="text" />
<button onClick={onButtonClick}>Focus the input</button>
</div>
);
}
自定义引用公开的实例值。
import { forwardRef, useImperativeHandle, useRef } from 'react';
const FancyInput = forwardRef((props, ref) => {
const inputRef = useRef();
useImperativeHandle(ref, () => ({
focus: () => {
inputRef.current.focus();
},
}));
return <input ref={inputRef} />;
});
function App() {
const fancyInputRef = useRef();
return (
<div>
<FancyInput ref={fancyInputRef} />
<button onClick={() => fancyInputRef.current.focus()}>Focus input</button>
</div>
);
}
与 DOM 布局同步。
import { useEffect, useLayoutEffect, useRef, useState } from 'react';
function MeasureWidth() {
const ref = useRef();
const [width, setWidth] = useState(0);
useLayoutEffect(() => {
setWidth(ref.current.offsetWidth);
}, []);
return (
<div>
<div ref={ref} style={{ width: '50%' }}>
Resize the window to see the effect.
</div>
<p>Width: {width}px</p>
</div>
);
}
在 React DevTools 中显示自定义标签。
import { useDebugValue, useState } from 'react';
function useFriendStatus(friendID) {
const [isOnline, setIsOnline] = useState(null);
useDebugValue(isOnline ? 'Online' : 'Offline');
// Simulate an asynchronous operation
setTimeout(() => setIsOnline(Math.random() > 0.5), 1000);
return isOnline;
}
function FriendStatus({ friendID }) {
const isOnline = useFriendStatus(friendID);
if (isOnline === null) {
return 'Loading...';
}
return isOnline ? 'Online' : 'Offline';
}
从 API 获取数据。
import { useEffect, useState } from 'react';
function useFetch(url) {
const [data, setData] = useState(null);
const [loading, setLoading] = useState(true);
useEffect(() => {
fetch(url)
.then(response => response.json())
.then(data => {
setData(data);
setLoading(false);
});
}, [url]);
return { data, loading };
}
function App() {
const { data, loading } = useFetch('https://jsonplaceholder.typicode.com/posts');
if (loading) {
return <p>Loading...</p>;
}
return (
<ul>
{data.map(post => (
<li key={post.id}>{post.title}</li>
))}
</ul>
);
}
使用本地存储管理状态。
import { useState } from 'react';
function useLocalStorage(key, initialValue) {
const [storedValue, setStoredValue] = useState(() => {
try {
const item = window.localStorage.getItem(key);
return item ? JSON.parse(item) : initialValue;
} catch (error) {
console.error(error);
return initialValue;
}
});
const setValue = (value) => {
try {
const valueToStore = value instanceof Function ? value(storedValue) : value;
setStoredValue(valueToStore);
window.localStorage.setItem(key, JSON.stringify(valueToStore));
} catch (error) {
console.error(error);
}
};
return [storedValue, setValue];
}
function App() {
const [name, setName] = useLocalStorage('name', 'Bob');
return (
<div>
<input value={name} onChange={(e) => setName(e.target.value)} />
<p>Hello, {name}!</p>
</div>
);
}
随着时间的推移对值进行去抖。
import { useEffect, useState } from 'react';
function useDebounce(value, delay) {
const [debouncedValue, setDebouncedValue] = useState(value);
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value);
}, delay);
return () => {
clearTimeout(handler);
};
}, [value, delay]);
return debouncedValue;
}
function App() {
const [text, setText] = useState('');
const debouncedText = useDebounce(text, 500);
return (
<div>
<input value={text} onChange={(e) => setText(e.target.value)} />
<p>Debounced Value: {debouncedText}</p>
</div>
);
}
存储变量的先前值。
import { useEffect, useRef } from 'react';
function usePrevious(value) {
const ref = useRef();
useEffect(() => {
ref.current = value;
}, [value]);
return ref.current;
}
function App() {
const [count, setCount] = useState(0);
const previousCount = usePrevious(count);
return (
<div>
<button onClick={() => setCount(count + 1)}>Count: {count}</button>
<p>Previous Count: {previousCount}</p>
</div>
);
}
跟踪窗口大小。
import { useEffect, useState } from 'react';
function useWindowSize() {
const [size, setSize] = useState({ width: window.innerWidth, height: window.innerHeight });
useEffect(() => {
const handleResize = () => {
setSize({ width: window.innerWidth, height: window.innerHeight });
};
window.addEventListener('resize', handleResize);
return () => window.removeEventListener('resize', handleResize);
}, []);
return size;
}
function App() {
const { width, height } = useWindowSize();
return (
<div>
<p>Width: {width}px</p>
<p>Height: {height}px</p>
</div>
);
}
检测元素是否悬停。
import { useCallback, useState } from 'react';
function useHover() {
const [hovered, setHovered] = useState(false);
const onMouseOver = useCallback(() => setHovered(true), []);
const onMouseOut = useCallback(() => setHovered(false), []);
return { hovered, onMouseOver, onMouseOut };
}
function HoverComponent() {
const { hovered, onMouseOver, onMouseOut } = useHover();
return (
<div onMouseOver={onMouseOver} onMouseOut={onMouseOut}>
{hovered ? 'Hovering' : 'Not Hovering'}
</div>
);
}
跟踪在线状态。
import { useEffect, useState } from 'react';
function useOnlineStatus() {
const [isOnline, setIsOnline] = useState(navigator.onLine);
useEffect(() => {
const handleOnline = () => setIsOnline(true);
const handleOffline = () => setIsOnline(false);
window.addEventListener('online', handleOnline);
window.addEventListener('offline', handleOffline);
return () => {
window.removeEventListener('online', handleOnline);
window.removeEventListener('offline', handleOffline);
};
}, []);
return isOnline;
}
function App() {
const isOnline = useOnlineStatus();
return <div>{isOnline ? 'Online' : 'Offline'}</div>;
}
附加事件监听器。
import { useEffect, useRef } from 'react';
function useEventListener(eventName, handler, element = window) {
const savedHandler = useRef();
useEffect(() => {
savedHandler.current = handler;
}, [handler]);
useEffect(() => {
const eventListener = (event) => savedHandler.current(event);
element.addEventListener(eventName, eventListener);
return () => {
element.removeEventListener(eventName, eventListener);
};
}, [eventName, element]);
}
function App() {
useEventListener('click', () => alert('Window clicked!'));
return <div>Click anywhere!</div>;
}
设置具有动态延迟的间隔。
import { useEffect, useRef } from 'react';
function useInterval(callback, delay) {
const savedCallback = useRef();
useEffect(() => {
savedCallback.current = callback;
}, [callback]);
useEffect(() => {
function tick() {
savedCallback.current();
}
if (delay !== null) {
const id = setInterval(tick, delay);
return () => clearInterval(id);
}
}, [delay]);
}
function Timer() {
const [count, setCount] = useState(0);
useInterval(() => setCount(count + 1), 1000);
return <div>Count: {count}</div>;
}
设置超时。
import { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
return (
<div>
<button onClick={() => setCount(count + 1)}>Increment</button>
<p>Count: {count}</p>
</div>
);
}
检测组件外部的点击。
import { useEffect, useState } from 'react';
function DataFetcher() {
const [data, setData] = useState(null);
useEffect(() => {
fetch('https://api.example.com/data')
.then(response => response.json())
.then(data => setData(data));
}, []);
return <div>Data: {data ? JSON.stringify(data) : 'Loading...'}</div>;
}
处理剪贴板操作。
import { useContext } from 'react';
import { ThemeContext } from './ThemeContext';
function ThemedButton() {
const theme = useContext(ThemeContext);
return <button style={{ background: theme.background }}>Click me</button>;
}
管理深色模式偏好。
import { useReducer } from 'react';
const initialState = { count: 0 };
function reducer(state, action) {
switch (action.type) {
case 'increment':
return { count: state.count + 1 };
case 'decrement':
return { count: state.count - 1 };
default:
throw new Error();
}
}
function Counter() {
const [state, dispatch] = useReducer(reducer, initialState);
return (
<div>
<button onClick={() => dispatch({ type: 'decrement' })}>-</button>
<span>{state.count}</span>
<button onClick={() => dispatch({ type: 'increment' })}>+</button>
</div>
);
}
在布尔值之间切换。
import { useCallback, useState } from 'react';
function CallbackComponent() {
const [count, setCount] = useState(0);
const increment = useCallback(() => {
setCount(count + 1);
}, [count]);
return <button onClick={increment}>Count: {count}</button>;
}
在浅色和深色主题之间切换。
import { useMemo, useState } from 'react';
function Fibonacci() {
const [num, setNum] = useState(1);
const fib = useMemo(() => {
const computeFib = (n) => (n <= 1 ? n : computeFib(n - 1) + computeFib(n - 2));
return computeFib(num);
}, [num]);
return (
<div>
<button onClick={() => setNum(num + 1)}>Next Fibonacci</button>
<p>Fibonacci of {num} is {fib}</p>
</div>
);
}
查询媒体属性。
import { useRef } from 'react';
function TextInputWithFocusButton() {
const inputEl = useRef(null);
const onButtonClick = () => {
inputEl.current.focus();
};
return (
<div>
<input ref={inputEl} type="text" />
<button onClick={onButtonClick}>Focus the input</button>
</div>
);
}
锁定正文卷轴。
import { forwardRef, useImperativeHandle, useRef } from 'react';
const FancyInput = forwardRef((props, ref) => {
const inputRef = useRef();
useImperativeHandle(ref, () => ({
focus: () => {
inputRef.current.focus();
},
}));
return <input ref={inputRef} />;
});
function App() {
const fancyInputRef = useRef();
return (
<div>
<FancyInput ref={fancyInputRef} />
<button onClick={() => fancyInputRef.current.focus()}>Focus input</button>
</div>
);
}
检测按键。
import { useEffect, useLayoutEffect, useRef, useState } from 'react';
function MeasureWidth() {
const ref = useRef();
const [width, setWidth] = useState(0);
useLayoutEffect(() => {
setWidth(ref.current.offsetWidth);
}, []);
return (
<div>
<div ref={ref} style={{ width: '50%' }}>
Resize the window to see the effect.
</div>
<p>Width: {width}px</p>
</div>
);
}
更新文档标题。
import { useDebugValue, useState } from 'react';
function useFriendStatus(friendID) {
const [isOnline, setIsOnline] = useState(null);
useDebugValue(isOnline ? 'Online' : 'Offline');
// Simulate an asynchronous operation
setTimeout(() => setIsOnline(Math.random() > 0.5), 1000);
return isOnline;
}
function FriendStatus({ friendID }) {
const isOnline = useFriendStatus(friendID);
if (isOnline === null) {
return 'Loading...';
}
return isOnline ? 'Online' : 'Offline';
}
处理悬停状态。
import { useEffect, useState } from 'react';
function useFetch(url) {
const [data, setData] = useState(null);
const [loading, setLoading] = useState(true);
useEffect(() => {
fetch(url)
.then(response => response.json())
.then(data => {
setData(data);
setLoading(false);
});
}, [url]);
return { data, loading };
}
function App() {
const { data, loading } = useFetch('https://jsonplaceholder.typicode.com/posts');
if (loading) {
return <p>Loading...</p>;
}
return (
<ul>
{data.map(post => (
<li key={post.id}>{post.title}</li>
))}
</ul>
);
}
检索地理位置。
import { useState } from 'react';
function useLocalStorage(key, initialValue) {
const [storedValue, setStoredValue] = useState(() => {
try {
const item = window.localStorage.getItem(key);
return item ? JSON.parse(item) : initialValue;
} catch (error) {
console.error(error);
return initialValue;
}
});
const setValue = (value) => {
try {
const valueToStore = value instanceof Function ? value(storedValue) : value;
setStoredValue(valueToStore);
window.localStorage.setItem(key, JSON.stringify(valueToStore));
} catch (error) {
console.error(error);
}
};
return [storedValue, setValue];
}
function App() {
const [name, setName] = useLocalStorage('name', 'Bob');
return (
<div>
<input value={name} onChange={(e) => setName(e.target.value)} />
<p>Hello, {name}!</p>
</div>
);
}
跟踪滚动位置。
import { useEffect, useState } from 'react';
function useDebounce(value, delay) {
const [debouncedValue, setDebouncedValue] = useState(value);
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value);
}, delay);
return () => {
clearTimeout(handler);
};
}, [value, delay]);
return debouncedValue;
}
function App() {
const [text, setText] = useState('');
const debouncedText = useDebounce(text, 500);
return (
<div>
<input value={text} onChange={(e) => setText(e.target.value)} />
<p>Debounced Value: {debouncedText}</p>
</div>
);
}
在组件卸载时运行函数。
import { useEffect, useRef } from 'react';
function usePrevious(value) {
const ref = useRef();
useEffect(() => {
ref.current = value;
}, [value]);
return ref.current;
}
function App() {
const [count, setCount] = useState(0);
const previousCount = usePrevious(count);
return (
<div>
<button onClick={() => setCount(count + 1)}>Count: {count}</button>
<p>Previous Count: {previousCount}</p>
</div>
);
}
检测元素外部的点击。
import { useEffect, useState } from 'react';
function useWindowSize() {
const [size, setSize] = useState({ width: window.innerWidth, height: window.innerHeight });
useEffect(() => {
const handleResize = () => {
setSize({ width: window.innerWidth, height: window.innerHeight });
};
window.addEventListener('resize', handleResize);
return () => window.removeEventListener('resize', handleResize);
}, []);
return size;
}
function App() {
const { width, height } = useWindowSize();
return (
<div>
<p>Width: {width}px</p>
<p>Height: {height}px</p>
</div>
);
}
对回调函数进行去抖动。
import { useCallback, useState } from 'react';
function useHover() {
const [hovered, setHovered] = useState(false);
const onMouseOver = useCallback(() => setHovered(true), []);
const onMouseOut = useCallback(() => setHovered(false), []);
return { hovered, onMouseOver, onMouseOut };
}
function HoverComponent() {
const { hovered, onMouseOver, onMouseOut } = useHover();
return (
<div onMouseOver={onMouseOver} onMouseOut={onMouseOut}>
{hovered ? 'Hovering' : 'Not Hovering'}
</div>
);
}
随着时间的推移限制值。
import { useEffect, useState } from 'react';
function useOnlineStatus() {
const [isOnline, setIsOnline] = useState(navigator.onLine);
useEffect(() => {
const handleOnline = () => setIsOnline(true);
const handleOffline = () => setIsOnline(false);
window.addEventListener('online', handleOnline);
window.addEventListener('offline', handleOffline);
return () => {
window.removeEventListener('online', handleOnline);
window.removeEventListener('offline', handleOffline);
};
}, []);
return isOnline;
}
function App() {
const isOnline = useOnlineStatus();
return <div>{isOnline ? 'Online' : 'Offline'}</div>;
}
仅在更新时运行效果，而不是在安装时运行效果。
import { useEffect, useRef } from 'react';
function useEventListener(eventName, handler, element = window) {
const savedHandler = useRef();
useEffect(() => {
savedHandler.current = handler;
}, [handler]);
useEffect(() => {
const eventListener = (event) => savedHandler.current(event);
element.addEventListener(eventName, eventListener);
return () => {
element.removeEventListener(eventName, eventListener);
};
}, [eventName, element]);
}
function App() {
useEventListener('click', () => alert('Window clicked!'));
return <div>Click anywhere!</div>;
}
管理本地存储中的状态
import { useEffect, useRef } from 'react';
function useInterval(callback, delay) {
const savedCallback = useRef();
useEffect(() => {
savedCallback.current = callback;
}, [callback]);
useEffect(() => {
function tick() {
savedCallback.current();
}
if (delay !== null) {
const id = setInterval(tick, delay);
return () => clearInterval(id);
}
}, [delay]);
}
function Timer() {
const [count, setCount] = useState(0);
useInterval(() => setCount(count + 1), 1000);
return <div>Count: {count}</div>;
}
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