text: import React from "react";
  import ReactDOM from "react-dom";
  
  class Index extends React.Component {
    constructor(props) {
      document.title = "主页";
      super(props);
    }
  
    render() {
      return (
        <div className="index">
          <h2>HELLO WORLD</h2>
        </div>
      );
    }
  }
  
  ReactDOM.render(<Index />, document.querySelector("#init"));
  