devServer.js

const path = require( 'path' );
const express = require( 'express' );
const webpack = require( 'webpack' );
const config = require( './webpack.config.dev' );

const app = express();
const compiler = webpack( config );

const port = process.env.PORT || 8000;

app.use( require( 'webpack-dev-middleware' )( compiler, {
  noInfo: true,
  publicPath: config.output.publicPath,
}));

app.use( require( 'webpack-hot-middleware' )( compiler ));

app.get( '*', function serveStatic( req, res ) {
  res.sendFile( path.join( __dirname, 'example/src/index.html' ));
});

app.listen( port, 'localhost', function useLocalhost( err ) {
  if ( err ) {
    console.log( err );
    return;
  }

  console.log( `Listening at http://localhost:${port}` );
});