1. 修改项目结构  2. App.js（相当于vue中的.vue文件） ~~~ import React, { Component } from 'react'; class App extends Component { // 固定格式返回一个html1 render() { return ( <div className="App"> hello world </div> ); } } export default App; ~~~ 3. index.js ~~~ import React from 'react'; import ReactDOM from 'react-dom'; import App from './pages/App'; ReactDOM.render(<App />, document.getElementById('root')); ~~~