Empty Pipes

Fast ES6 Development Using webpack-dev-server

  • 06 Dec 2016
  • |
  • javascript
  • es6
  • |


Switching from gulp and webpack-stream to webpack-dev-server reduces the rebuild time for a 5500-line javascript project from ~11s to ~1.3 seconds.


Whenever I create a javascript project, I do it using a very uniform directory structure and configuration, as outlined in a previous blog post. With this configuration, all the source files are transpiled using babel and bundled using the webpack-stream module as part of a step in the build process managed by gulp.

This is great because then I can run gulp serve and have it recompile and reload the resulting web page whenever I make any changes to the source code in app/scripts.

This works like a charm until the source code and dependencies get to any appreciable size. As more and more files need to be transpiled, the process gets slower and slower until at about ~10 seconds, it starts to get annoying:

[BS] 3 files changed (main.js, playground.js, worker.js)
[08:31:20] Finished 'scripts' after 11 s

So how can this be sped up? Easy, stop using gulp and webpack-stream and switch to the…

Webpack dev server

The webpack dev server runs in its own terminal and watches the source files listed in its config file (webpack.config.js). When one of the files changes, it recreates the output files specified in its config and reloads the web page. I run it using the following command line:

webpack-dev-server --content-base app --display-exclude --profile --inline | grep -v "\\[\\d*\\]"

The grep at the end is to filter out some of the [overly] verbose output that webpack produces. So how long does it take to regenerate the code when a source file is changed?

Version: webpack 1.12.15
Time: 1296ms
chunk    {0} main.js (main) 4.61 MB

This is about 10x faster than the configuration using gulp and webpack-stream.

The resulting web page can be found at http://localhost:8080/index.html

The only thing I needed to change in my webpack.config.js file was to add output: { publicPath: '/scripts/'}. This is because my index.html file loads the compiled scripts from the scripts directory:

<script src='scripts/playground.js'></script>

Below is the entire webpack.config.js for this project. Notice that there’s multiple different targets being built including a worker script that can be used in a web worker to do compute intensive tasks off of the main UI thread.

Other notable sights include the devtool: "cheap-source-map" entry to make sure we can easily see the source code when debugging.

var path = require('path');
var webpack = require('webpack');

module.exports = {
  context: __dirname + '/app',
  entry: {
      playground: ['./scripts/playground.jsx'],
      main: ['./scripts/main.jsx'],
      worker: ['./scripts/worker.js']
  devtool: "cheap-source-map",
  output: {
    path: __dirname + '/build',
    publicPath: '/scripts/',
    filename: '[name].js',
    libraryTarget: 'umd',
    library: '[name]'
  module: {
    loaders: [
        test: /\.jsx?$/,
        //exclude: /node_modules/,
        include: [path.resolve(__dirname, 'app/scripts')],
        loader: 'babel-loader',
        query: {
          presets: ['es2015', 'react']
      }, {
        test: /\.css$/,
        loader: 'style!css'
    postLoaders: [
            include: path.resolve(__dirname, 'node_modules/pixi.js'),
            loader: 'transform?brfs'
    externals: {

    resolve: {
      extensions: ['.js', '.jsx']