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() {let element = nullif (this.state.isLogin) {if (this.state.isLogin) {element = ( < UserGree > < /UserGree>)}else {element = ( < UserLogin > < /UserLogin>)}return ( <div ><h1 > 我是头部 < /h1> { element } <h1 > 三元运算符的 < /h1>  { this.state.isLogin ?  <UserGree > < /UserGree>: < UserLogin > < /UserLogin >} <h1 > 我是尾部 < /h1> < /div >)}}}//console.log("这是渲染函数")ReactDOM.render( < ParentCom / > , document.querySelector("#root"))

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