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Universal: Chapter 0

The purpose of this chapter is to setup a development environment to start working on our universal app. We will cover Webpack, Babel, PostCSS, ESLint and we will create a DevServer.

Branch: To see the commits of this chapter checkout this branch.

Release: To skip this chapter just clone this release.


Go ahead, create a new directory and jump in

mkdir universal-app && cd universal-app

Initialize a git repository

git init

Create a new branch setup

git checkout -b setup

Set node version to v6

nvm install 6 && nvm use 6


echo 'Javascript Universal App' > README.md

Initialize npm (go thru the interactive setup)

npm init

Ignore node_modules

echo node_modules > .gitignore

You are all set!

Diff: to see the diff for this step click here.

Fast-forward: git clone --branch init https://github.com/cazala/universal-app.git --depth=1


Webpack is a widely used module bundler, and the first thing to setup

npm install webpack --save-dev

First create a /src and /dist directories

mkdir src && mkdir dist

Save the following file as webpack.config.js

var webpack = require('webpack')
var path = require('path')
module.exports = {  
  context: __dirname,  
  entry: './src/index.js',  
  output: {    
    path: path.resolve('dist'),    
    filename: 'bundle.js',  },  
    plugins: [ new webpack.NoErrorsPlugin() ],  
    resolve: {    
      extensions: ['', '.js', '.json'],    
      modulesDirectories: ['.', 'src', 'node_modules']  

Add /dist to the .gitignore file node_modules dist

Add build and start scripts to your package.json

"build": "webpack --config webpack.config.js",
"start": "node dist/bundle.js",

Test It Out:

Create the following index.js file inside /src:

console.log('hello world')

Now just npm run build and then npm run start

You should see a hello world in your console, and you will find that you 1 line src/index.js has become a 51 lines dist/bundle.js. Yay… right? This will pay off in the future tho, as we start plugging stuff into webpack.

Diff: to see the diff for this step click here.

Fast-forward: git clone --branch webpack https://github.com/cazala/universal-app.git --depth=1


Babel is a JavaScript compiler. It extends the language capabilities thru syntax transformers, we will need this in order to use ES2015 and React.

Get ready to install a truckload of dependencies

npm install --save babel-core babel-plugin-jsx-display-if babel-plugin-transform-object-rest-spread babel-polyfill babel-preset-es2015 babel-preset-react babel-register babel-runtime babel-loader

Add .babelrc to configure babel

  "presets": ["es2015", "react"],
  "plugins": [

And finally add loader to webpack.config.js so webpack transpiles all the .js files using babel (except the ones in node_modules)

module: {  
  loaders: [    
      test: /\.js$/,      
      loaders: ['babel'],      
      exclude: /node_modules/    

Test It Out:

Save the following as your src/index.js

const obj = { a: 1, b:2, c:3 }
const { a, ...rest } = obj
const spread = { ...rest, d: 4 }
console.log(rest) // { b:2, c: 3}
console.log(spread) // { b:2, c: 3, d: 4 }

Now npm run build and npm run start and you should see the rest and spread operators working (thus, babel is working)

Diff: to see the diff for this step click here.

Fast-forward: git clone --branch babel https://github.com/cazala/universal-app.git --depth=1


PostCSS is a tool for transforming CSS with JavaScript, like a Babel for CSS. We will set it up to let us work with autoprefixer, css modules (localized css classnames), css nesting, css variables and what not.

Again, get ready for installing a bunch of deps:

npm install --save-dev autoprefixer css-loader style-loader postcss-import postcss-loader postcss-mixins postcss-nested postcss-simple-vars

Add loaders to webpack.config.js so webpack loads all the .css and .scss files with style, css and postcss loaders.

This way we will be able to require(./styles.css)

  • style-loader: It adds a <style> tag to the <head> with the loaded style.

  • css-loader: It transform the css file with localized classnames (aka CSS Modules), applies minification and source-maps.

  • postcss-loader: It lets us use transformation plugins like autoprefixer, import, nested, and simple-vars, to have a sass\/less similar experience.

So lets add the loaders:

  test: /(\.scss|\.css)$/,
  loaders: ['style', 'css?sourceMap&modules&importLoaders=1&localIdentName=[name]__[local]___[hash:base64:5]', 'postcss']

Add the postcss plugins:

postcss: [

And add the extensions to resolve.extension

extensions: ['', '.js', '.json', '.css', 'scss'],

Test It Out:

Add the following index.css to /src

.red {
  color: red;

Add the following index.js to /src

import styles from './index.css'
console.log(styles) // { red: '...' }
window.onload = () => document.body.classList.add(styles.red)

And finally add this index.html at the root level (not to /src)

<script src='./dist/bundle.js'></script>
<body>Hello World</body>

Now run npm run build and open index.html

You should see that a <style> tag was added to the <head> with our css file, and the localized css classname index__red___3fvh6 was applied to the <body>, making the Hello World be red.

Diff: to see the diff for this step click here.

Fast-forward: git clone --branch postcss https://github.com/cazala/universal-app.git --depth=1


ESLint is a lint utility that will help us debug at coding time and write consistent code.

Yet again, another bigass npm install:

npm install --save-dev eslint babel-eslint eslint-config-standard eslint-config-standard-react eslint-plugin-babel eslint-plugin-import eslint-plugin-jsx-a11y eslint-plugin-promise eslint-plugin-react eslint-plugin-standard eslint-watch

Add a .eslintrc file to configure the linter, this is an example of the coding style that I use, but you can configure it to your needs, and there are tons of eslint plugins that you can choose from in npm:

  "env": {
    "browser": true,
    "node": true
  "parser": "babel-eslint",
  "extends": ["standard", "standard-react"],
  "rules": {
    "comma-dangle" : [0, "always-multiline"],
    "semi": [2, "never"],
    "no-extra-semi": 2,
    "jsx-quotes": [2, "prefer-single"],
    "react/jsx-boolean-value": [0, "always"],
    "react/jsx-max-props-per-line": [2, {"maximum": 4}],
    "react/self-closing-comp": 2,
    "react/jsx-indent-props": [2, 2],
    "react/sort-comp": 2

Test It Out:

Now, save the following as your src/index.js

const a = 1
const b = 2
const c = 3 // unused variable
console.log(a + b)

(also, you can delete the /index.html and /src/index.css from previous step if you still have them)

So now if you open src/index.js with an editor with eslint support (like Atom + Linter + ESLint Plugin) it should be working:

Diff: to see the diff for this step click here.

Fast-forward: git clone --branch eslint https://github.com/cazala/universal-app.git --depth=1


Finally, we will create a development server that will watch for changes in our files as we develop and serve them thru a web server, so we can see our work and debug as we code

npm install --save express
npm install --save-dev webpack-dev-middleware webpack-hot-middleware

Add the following file as dev-server.js:

var webpack = require('webpack')
var webpackDevMiddleware = require('webpack-dev-middleware')
var webpackHotMiddleware = require('webpack-hot-middleware')
var config = require('./webpack.config.js')
var Express = require('express')
var app = new Express()
var port = process.env.PORT || 9999
var compiler = webpack(config)
var dev = webpackDevMiddleware(compiler, { noInfo: true, publicPath: config.output.publicPath })
var hot = webpackHotMiddleware(compiler)


app.get('*', function (req, res) {
        <title>Webpack Development Server</title>
        <div id="root">Hello World</div>
      <script src="/bundle.js" async defer></script>

app.listen(port, (error) => {
  if (error) { console.error(error) return }
  console.info('Open up http://localhost:%s/ in your browser.', port)

Add a devtool property to webpack.config.js to generate source maps

devtool: 'cheap-module-eval-source-map',

Add webpack-hot-middleware’s client to your webpack.entry list

entry: [

Add a public path to your webpack.output, that’s where the Express will serve the bundle.

output: {
  path: path.resolve('dist'),
  filename: 'bundle.js',
  publicPath: '/'

Add webpack’s HotModuleReplacementPlugin to your webpack.plugins

plugins: [
  new webpack.HotModuleReplacementPlugin(),
  new webpack.NoErrorsPlugin()

You can also remove src/index.js if you still have it from previous step

Finally, add a script to your package.json’s scripts to start the dev-server

"dev-server": "node dev-server.js",

Test It Out:

Just npm run dev-server and open up localhost:9999, you should see a Hello World

Diff: to see the diff for this step click here.

Fast-forward: git clone --branch dev-server https://github.com/cazala/universal-app.git --depth=1