output: {
  path: path.join(__dirname, '/../dist/assets'),
  filename: 'app.js',
  publicPath: defaultSettings.publicPath,
  // 添加 chunkFilename
  chunkFilename: '[name].[chunkhash:5].chunk.js',
},

ReactDOM.render(
 (
  <Router history={browserHistory}>
   {/* 主页 */}
   <Route path="/" component={App}>
    {/* 默认 */}
    <IndexRoute component={HomePage} />

    {/* baidu */}
    <Route path="/baidu" component={BaiduPage}>
     <Route path="result" component={BaiduResultPage} />
     <Route path="frequency" component={BaiduFrequencyPage} />
    </Route>

    {/* 404 */}
    <Route path='/404' component={NotFoundPage} />
    
    {/* 其他重定向到 404 */}
    <Redirect from='*' to='/404' />
   </Route>
  </Router>
 ), document.getElementById('app')
);

const rootRoute = {
 path: '/',
 indexRoute: {
  getComponent(nextState, cb) {
   require.ensure([], (require) => {
    cb(null, require('components/layer/HomePage'))
   }, 'HomePage')
  },
 },
 getComponent(nextState, cb) {
  require.ensure([], (require) => {
   cb(null, require('components/Main'))
  }, 'Main')
 },
 childRoutes: [
  require('./routes/baidu'),
  require('./routes/404'),
  require('./routes/redirect')
 ]
}

ReactDOM.render(
 (
  <Router
   history={browserHistory}
   routes={rootRoute}
   />
 ), document.getElementById('app')
);

require.ensure(dependencies, callback, chunkName)

routes/
├── 404
│  └── index.js
├── baidu
│  ├── index.js
│  └── routes
│    ├── frequency
│    │  └── index.js
│    └── result
│      └── index.js
└── redirect
  └── index.js

module.exports = {
 path: '404',

 getComponent(nextState, cb) {
  require.ensure([], (require) => {
   cb(null, require('components/layer/NotFoundPage'))
  }, 'NotFoundPage')
 }
}

module.exports = {
 path: 'baidu',

 getChildRoutes(partialNextState, cb) {
  require.ensure([], (require) => {
   cb(null, [
    require('./routes/result'),
    require('./routes/frequency')
   ])
  })
 },

 getComponent(nextState, cb) {
  require.ensure([], (require) => {
   cb(null, require('components/layer/BaiduPage'))
  }, 'BaiduPage')
 }
}

module.exports = {
 path: 'frequency',

 getComponent(nextState, cb) {
  require.ensure([], (require) => {
   cb(null, require('components/layer/BaiduFrequencyPage'))
  }, 'BaiduFrequencyPage')
 }
}

<Router history={browserHistory}>
   <Route path="/" component={App}>
    {/* home */}
    <IndexRoute component={HomePage} />

    <Route path="/baidu" component={BaiduPage}>
     <Route path="result" component={BaiduResultPage} />
     <Route path="frequency" component={BaiduFrequencyPage} />
    </Route>

    <Route path='/404' component={NotFoundPage} />
    {/* 如果都不匹配，重定向到 404 */}
    <Redirect from='*' to='/404' />
   </Route>
  </Router>

module.exports = {
 path: '*',
 onEnter: (_, replaceState) => replaceState(null, "/404")
}

getComponent(nextState, cb) {
  require.ensure([], (require) => {
   // 在后面加 .default
   cb(null, require('components/layer/ReportPage')).default
  }, 'ReportPage')
}