index.js

import React from 'react';
import ReactDOM from 'react-dom';function UserGree(props) {return ( < h1 > 欢迎登陆 < /h1>)}function UserLogin(props) {return ( < h1 > 请先登陆 < /h1>)}class ParentCom extends React.Component {constructor(props) {super(props)this.state = {isLogin: true}}render() {if (this.state.isLogin) {if (this.state.isLogin) {return ( < UserGree > < /UserGree>)}else {return ( < UserLogin > < /UserLogin>)}}}}//console.log("这是渲染函数")ReactDOM.render( < ParentCom / > , document.querySelector("#root"))

运行结果