自定义hooks实现在useState改变值之后立刻获取到最新的值

import React from 'react'
function App () {
  let [count, setCount] = React.useState(0)
​
  const add =  () =>  {
    setCount(count + 1)
    console.log(count)
  }
​
  return (
​
    <div>
      <h1>{count}</h1>
      <button onClick={add}>点我加 1 </button>
    </div>
​
  )
}
export default App;

以上代码每次点击按钮得到的 count 值都是上一次的值

再来看看以下代码

import React from 'react'
import useSyncCallback from './hooks/hook'
function App () {
  let [count, setCount] = React.useState(0)
  
  const add =  () =>  {
    setCount(count + 1)
    fnc()
  }
  const fnc = useSyncCallback(() => {
    console.log(count)
  })
​
  return (
    <div>
      <h1>{count}</h1>
      <button onClick={add}>点我加 1 </button>
    </div>
  )
}
export default App;
​

以上代码可以得到更新之后的值

下面写上 useSyncCallback 函数的实现

import { useEffect, useState, useCallback } from "react";
​
const useSyncCallback = (callback) => {
  const [proxyState, setProxyState] = useState({ current: false });
​
  const Func = useCallback(() => {
    setProxyState({ current: true });
  }, [proxyState]);
​
  useEffect(() => {
    if (proxyState.current === true) setProxyState({ current: false });
  }, [proxyState]);
​
  useEffect(() => {
    proxyState.current && callback();
  });
​
  return Func;
};
​
export default useSyncCallback;

标签：count,const,自定义,hooks,useSyncCallback,proxyState,current,useState
来源： https://www.cnblogs.com/liujis/p/16053144.html