require.ensure([],(require) => {
     let A = require('./a.js').default;
})

import React, {Component} from 'react';
export default class Container extends Component {
  constructor() {
    super();
    this.state = {
      currentComponent: null
    }
  }

  doSomething = () => {
    require.ensure(['./app2'], (require) => {
      const Comp = require('./app2');
      this.setState({
        currentComponent: <Comp/>
      })
    })
  };

  render() {
    return (
      <div>
        <span onClick={this.doSomething} style={{border: "1px solid #000"}}>点击后，按需加载如下模块</span>
        {this.state.currentComponent}
      </div>
    )
  }
}

import React from 'react'
export default class Hello extends React.Component {
  render(){
    return (
      <div>Hello</div>
    )
  }
}
//warning:这一句必须加上,因为在require.ensure中使用了require引入模块
module.exports = Hello;