title: How to configure webpack dev server with react router dom v4?
body: <p>This is the code of my webpack configuration: </p>
  
  <pre><code>const compiler = webpack({
    entry: ['whatwg-fetch', path.resolve(__dirname, 'js', 'app.js')], 
    module: {
      loaders: [
        {
          exclude: /node_modules/, 
          test: /\.js$/, 
          loader: 'babel',
        },
      ],
    },
    output: {filename: 'app.js', path: '/'}, 
  });
  
  const app = new WebpackDevServer(compiler, {
    contentBase: '/public/', 
    proxy: {'/graphql': `http://localhost:${GRAPHQL_PORT}`},
    publicPath: '/js/',
    stats: {colors: true}, 
  });
  
  app.use('/', express.static(path.resolve(__dirname, 'public')));
  </code></pre>
  
  <p>Works fine, the app runs on localhost:3000/index.html but when I try to implement React Router dom v4. It doesn't work. This is the code:</p>
  
  <pre><code>const About = () =&gt; &lt;div&gt; &lt;h1&gt;About&lt;/h1&gt; &lt;/div&gt;
  
  ReactDOM.render(
     &lt;BrowserRouter&gt;
        &lt;div&gt;
        &lt;Route exact path='/' component={App}/&gt;
        &lt;Route  path='/about' component={About}/&gt;
        &lt;/div&gt;
      &lt;/BrowserRouter&gt;,
    mountNode
  );
  </code></pre>
  
  <p>This is the result on localhost:3000/ <a href="https://i.stack.imgur.com/SFFGk.png" rel="noreferrer"><img src="https://i.stack.imgur.com/SFFGk.png" alt="build.min.js"></a>
  And on localhost:3000/about. I get an error: Cannot GET /about . Not what I'm expecting, why would this not render?  <h1>About</h1>  </p>