text: import React from 'react';
  import ReactDOM from 'react-dom';
  import createHistory from 'history/createBrowserHistory';
  import app from './app-client';
  
  const history = createHistory();
  
  const render = !!module.hot ? ReactDOM.render : ReactDOM.hydrate;
  
  // 把根组件渲染到 DOM 树上
  render(app({ history }), window.document.getElementById('app'));
  