react-router-dom问题

Question

我在react-router 官网找的第一个基本demo 我用脚手架组件来实现遇到点问题

入口文件index.js
代码如下：
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import RouteMap from './router/routeMap'
import registerServiceWorker from './registerServiceWorker';

ReactDOM.render(<RouteMap/>, document.getElementById('root'));
registerServiceWorker();

路由文件routerMap.js
import React, {Component} from 'react'
import {BrowserRouter as Router, Route, Link} from 'react-router-dom'
import Home from '../components/Homepage/homepage'
import About from '../components/About/about'
import Topics from '../components/Topics/topics'

class RouteMap extends Component {

updateHandle() {
    console.log('每次router变化之后都会触发')
}

render() {
    return (
        <Router onUpdate={this.updateHandle.bind(this)}>
            <div>
                <ul>
                    <li><Link to="/">Home</Link></li>
                    <li><Link to="/about">About</Link></li>
                    <li><Link to="/topics">Topics</Link></li>
                </ul>

                <hr/>

                <Route exact path="/" component={Home}/>
                <Route path="/about" component={About}/>
                <Route path="/topics" component={Topics}/>
            </div>
        </Router>
    )
}

}

export default RouteMap

三个组件文件如图：

目录文件

结果报错了。。。

请问哪位大神分析下什么问题？谢谢