useMemo使用场景：消耗非常大的计算，例如递归

import {  useMemo, useState } from 'react';
// 缓存：消耗非常大的计算，例如递归
function fib(n){console.log('fib');if(n < 3)return 1;return fib(n-2) + fib(n-1);
}const App = () => {const [count1,setCount1] = useState(0);const [count2,setCount2] = useState(0);const result = useMemo(()=>{return fib(count1)},[count1])// const result = fib(count1);console.log('组件重新渲染了');return (<div className="home"><button type="primary" onClick={()=>setCount1(count1 + 1)}>count1值{count1}</button><br /><button type="primary" onClick={()=>setCount2(count2 + 1)}>count2值{count2}</button><br />{result}</div>)
}export default App