React中常见Hooks总结

React Hooks是React 16.8及更高版本引入的特性，它们可以让你在函数组件中使用state以及其他的React特性而无需写class。

以下是一些常用的React Hooks以及它们的简单描述和用法示例：

1. useState

import React, { useState } from 'react';
 
function Example() {
  // 声明一个叫 "count" 的 state 变量
  const [count, setCount] = useState(0);
 
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

2. useEffect

import React, { useState, useEffect } from 'react';
 
function Example() {
  const [count, setCount] = useState(0);
 
  // 类似于类组件中的componentDidMount和componentDidUpdate
  useEffect(() => {
    // 更新document的title
    document.title = `You clicked ${count} times`;
  });
 
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

3. useContext

import React, { useContext } from 'react';
import { ThemeContext } from './ThemeContext';
 
function Button() {
  const theme = useContext(ThemeContext);
 
  return (
    <button style={{ backgroundColor: theme.background }}>
      I am styled by theme context!
    </button>
  );
}

4. useReducer

import React, { useReducer } from 'react';
 
function Example() {
  // 类似于useState，但用于管理复杂的state
  const [state, dispatch] = useReducer(reducer, initialState);
 
  return (
    <div>
      <p>Count: {state.count}</p>
      <button onClick={() => dispatch({ type: 'increment' })}>
        Increment
      </button>
      <button onClick={() => dispatch({ type: 'decrement' })}>
        Decrement
      </button>
    </div>
  );
}
 
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();
  }
}

5. useCallback

import React, { useCallback } from 'react';
 
function Example() {
  const memoizedCallback = useCallback(() => {
    doSomething(a, b);
  }, [a, b]);
 
  return <SomeComponent onSomething={memoizedCallback} />;
}

6. useMemo

import React, { useMemo } from 'react';
 
function Example() {
  const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);
 
  return <div>{memoizedValue}</div>;
}

7. useRef