![[呲牙]](http://lf-web-assets.juejin.cn/obj/juejin-web/xitu_juejin_web/img/jj_emoji_2.cd1e2bd.png)
![[衰]](http://lf-web-assets.juejin.cn/obj/juejin-web/xitu_juejin_web/img/jj_emoji_34.cf5b4d5.png)
获得徽章 9
- import React, { useEffect, useState } from "react";
function App() {
const [appNum, setAppNum] = useState(100);
console.log("父组件 更新了");
const SonComponent = React.memo(function Son() {
console.log("SonComponent 更新了");
return <div>SonComponent</div>;
});
useEffect(() => {
setTimeout(() => {
setAppNum(150);
}, 3000);
}, []);
return (
<div className="App">
this is app {appNum}
<SonComponent />
</div>
);
}
export default App; 为什么这段代码用了React.memo不生效而把SonComponent组件单独放在另一个文件中却能生效？展开7点赞
