text: 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