content: import React from 'react'
  import {
    BrowserRouter as Router,
    Route,
    Link
  } from 'react-router-dom'
  
  const BasicExample = () => (
    <Router>
      <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>
  )
  
  const Home = () => (
    <div>
      <h2>Home</h2>
    </div>
  )
  
  const About = () => (
    <div>
      <h2>About</h2>
    </div>
  )
  
  const Topics = ({ match }) => (
    <div>
      <h2>Topics</h2>
      <ul>
        <li>
          <Link to={`${match.url}/rendering`}>
            Rendering with React
          </Link>
        </li>
        <li>
          <Link to={`${match.url}/components`}>
            Components
          </Link>
        </li>
        <li>
          <Link to={`${match.url}/props-v-state`}>
            Props v. State
          </Link>
        </li>
      </ul>
  
      <Route path={`${match.url}/:topicId`} component={Topic}/>
      <Route exact path={match.url} render={() => (
        <h3>Please select a topic.</h3>
      )}/>
    </div>
  )
  
  const Topic = ({ match }) => (
    <div>
      <h3>{match.params.topicId}</h3>
    </div>
  )
  
  export default BasicExample
  