React Hooks 全解: 常用 Hooks 及使用场景详解

React Hooks 是 React 16.8 版本引入的一项重要特性,它极大地简化和优化了函数组件的开发过程。 React 中常用的 10 个 Hooks,包括 useState、useEffect、useContext、useReducer、useCallback、useMemo、useRef、useLayoutEffect、useImperativeHandle 和 useDebugValue。这些 Hooks 涵盖了状态管理、副作用处理、性能优化、DOM 操作等各个方面,为开发者提供了强大的工具,大幅提高了开发效率和代码质量。

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无论您是 React 新手还是老手,全面而深入的 Hooks 知识,帮助您更好地掌握 React 函数组件的开发技巧。让我们一起探索 React Hooks 的强大功能,提升您的 React 开发水平。

useState

使用场景: 管理组件内部的状态

示例代码:

import { useState } from 'react';function Counter() {const [count, setCount] = useState(0);return (<div><p>You clicked {count} times</p><button onClick={() => setCount(count + 1)}>Click me</button></div>);
}

useEffect

使用场景: 处理组件生命周期,例如数据获取、订阅、手动更改 DOM 等

示例代码:

import { useState, useEffect } from 'react';function FetchData() {const [data, setData] = useState([]);useEffect(() => {async function fetchData() {const response = await fetch('/api/data');const data = await response.json();setData(data);}fetchData();}, []);return (<div><h1>Fetched Data</h1><ul>{data.map((item) => (<li key={item.id}>{item.name}</li>))}</ul></div>);
}

useContext

使用场景: 跨组件传递数据,避免"prop drilling"

示例代码:

import { createContext, useContext } from 'react';const ThemeContext = createContext('light');function App() {return (<ThemeContext.Provider value="dark"><ThemedButton /></ThemeContext.Provider>);
}function ThemedButton() {const theme = useContext(ThemeContext);return <button style={{ backgroundColor: theme === 'dark' ? 'black' : 'white' }}>Theme Button</button>;
}

useReducer

使用场景: 管理复杂的状态逻辑

示例代码:

import { useReducer } from 'react';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, { count: 0 });return (<div><p>Count: {state.count}</p><button onClick={() => dispatch({ type: 'increment' })}>+</button><button onClick={() => dispatch({ type: 'decrement' })}>-</button></div>);
}

useCallback

使用场景: 缓存函数引用,优化性能

示例代码:

import { useState, useCallback } from 'react';function Parent() {const [count, setCount] = useState(0);const handleClick = useCallback(() => {setCount(count + 1);}, [count]);return (<div><p>Count: {count}</p><ChildComponent onClick={handleClick} /></div>);
}function ChildComponent({ onClick }) {console.log('ChildComponent rendered');return <button onClick={onClick}>Increment</button>;
}

useMemo

使用场景: 缓存计算结果,优化性能

示例代码:

import { useState, useMemo } from 'react';function ExpensiveCalculation() {const [number, setNumber] = useState(0);const doubledNumber = useMemo(() => {return slowlyDoubleNumber(number);}, [number]);return (<div><input type="number" value={number} onChange={(e) => setNumber(parseInt(e.target.value))} /><p>Doubled number: {doubledNumber}</p></div>);
}function slowlyDoubleNumber(n) {// 模拟一个耗时的计算let i = 0;while (i < 1000000000) i++;return n * 2;
}

useRef

使用场景: 获取 DOM 元素引用,保存可变状态

示例代码:

import { useRef } from 'react';function FocusInput() {const inputRef = useRef(null);const handleClick = () => {inputRef.current.focus();};return (<div><input type="text" ref={inputRef} /><button onClick={handleClick}>Focus Input</button></div>);
}

useLayoutEffect

使用场景: 处理 DOM 操作,需要同步执行

示例代码:

import { useLayoutEffect, useRef } from 'react';function MeasureElement() {const elementRef = useRef(null);useLayoutEffect(() => {const element = elementRef.current;console.log('Element width:', element.offsetWidth);}, []);return <div ref={elementRef}>This is the element to measure</div>;
}

useImperativeHandle

使用场景: 暴露组件实例方法给父组件

示例代码:

import { forwardRef, useImperativeHandle, useRef } from 'react';const CustomInput = forwardRef((props, ref) => {const inputRef = useRef(null);useImperativeHandle(ref, () => ({focus: () => {inputRef.current.focus();}}));return <input type="text" ref={inputRef} />;
});function App() {const inputRef = useRef(null);const handleClick = () => {inputRef.current.focus();};return (<div><CustomInput ref={inputRef} /><button onClick={handleClick}>Focus Input</button></div>);
}

useDebugValue

使用场景: 为自定义 Hooks 提供调试标签

示例代码:

import { useState, useDebugValue } from 'react';function useCustomHook() {const [state, setState] = useState(0);useDebugValue(`Current state: ${state}`);// 自定义 Hook 的其他逻辑return [state, setState];
}