reactjs – React Routing Async

import React from 'react';
import { Route, IndexRoute } from 'react-router';

import Index from './containers/home';
import App from './components/app';

//for single Component lazy load use this
const ContactComponent = () => {
  return {
      getComponent: (location, callback)=> {
        require.ensure([], require => {
          callback(null, require('./components/Contact')["default"]);
        }, 'Contact');
      }
    }
};

//for multiple componnets
 const groupedComponents = (pageName) => {
  return {
      getComponent: (location, callback)=> {
        require.ensure([], require => {
          switch(pageName){
            case 'about' :
                callback(null, require( "./components/about" )["default"]);
                    break ;
            case 'tos' :
                callback(null, require( "./components/tos" )["default"]);
                    break ;
          }
        }, "groupedComponents");
      }
    }
};
export default(
  <Route path="/" component={App}>
    <IndexRoute component={Index} />
    <Route path="/contact" {...ContactComponent()} />
    <Route path="/about" {...groupedComponents('about')} />
    <Route path="/tos" {...groupedComponents('tos')} />
  </Route>
);

if you want to reproduce, please indicate the source:
reactjs – React Routing Async - CodeDay