Getting Started

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From the blog:
ajv - The Fastest JSON Schema Validator - Interview with Evgeny Poberezkin

Before getting started, make sure you are using a recent version of Node.js. I recommend using at least the most recent LTS (long-term support) version. Before going further, you should have node and npm commands available at your terminal.

The completed configuration is available at GitHub. If you are unsure of something, refer there.

It is possible to get a more controlled environment by using a solution such as Vagrant or nvm. Vagrant comes with a performance penalty as it relies on a virtual machine. Vagrant is particularly useful in a team environment, though, as it gives you a predictable environment to develop against.

Setting Up the Project#

To get a starting point, we should create a directory for our project and set up a package.json there. npm uses that to manage project dependencies. Here are the basic commands:

mkdir webpack-demo
cd webpack-demo
npm init -y # -y generates *package.json*, skip for more control

You can tweak the generated package.json manually to make further changes to it. We'll be doing some changes through npm tool, but manual tweaks are acceptable. The official documentation explains various package.json options in more detail.

You can set those npm init defaults at ~/.npmrc.
This is a good place to set up version control using Git. You can create a commit per step and tag per chapter so it's easier to move back and forth if you want.

Installing Webpack#

Even though webpack can be installed globally (npm i webpack -g), I recommend maintaining it as a dependency of your project. This will avoid issues, as then you will have control over the exact version you are running.

The approach works nicely in Continuous Integration (CI) setups as well. A CI system can install your local dependencies, compile your project using them, and then push the result to a server.

To add webpack to our project, execute:

npm i [email protected] --save-dev # or just -D if you want to save typing

You should see webpack at your package.json devDependencies section after this. In addition to installing the package locally below the node_modules directory, npm also generates an entry for the executable.

We are using the most recent beta version of webpack 2 in this tutorial! You can drop that @beta part in the future. A lot of loaders and plugins may give peer dependency warnings as well.

Executing Webpack#

You can display the exact path of the executables using npm bin. Most likely it points at ./node_modules/.bin. Try executing webpack from there through terminal using node_modules/.bin/webpack or a similar command.

After executing, you should see a version, a link to the command line interface guide and a long list of options. We won't be using most of those, but it's good to know that this tool is packed with functionality, if nothing else.

webpack-demo $ node_modules/.bin/webpack
No configuration file found and no output filename configured via CLI option.
A configuration file could be named 'webpack.config.js' in the current directory.
Use --help to display the CLI options.
We can use --save and --save-dev to separate application and development dependencies. The former will install and write to package.json dependencies field whereas the latter will write to devDependencies instead.

Directory Structure#

As projects with just package.json are boring, we should set up something more concrete. To get started, we can implement a little website that loads some JavaScript, which we then build using webpack. After we progress a bit, we'll end up with a directory structure like this:

  • app/
    • index.js
    • component.js
  • build/
  • package.json
  • webpack.config.js

The idea is that we'll transform that app/ to as a bundle below build/. To make this possible, we should set up the assets needed and webpack.config.js.

Setting Up Assets#

As you never get tired of Hello world, we might as well model a variant of that. Set up a component like this:


export default function () {
  const element = document.createElement('h1');

  element.innerHTML = 'Hello world';

  return element;

Next, we are going to need an entry point for our application. It will simply require our component and render it through the DOM:


import component from './component';


Setting Up Webpack Configuration#

We'll need to tell webpack how to deal with the assets we just set up. For this purpose, we'll develop a webpack.config.js file. Webpack and its development server will be able to discover this file through convention.

To keep things simple to maintain, we'll be using html-webpack-plugin to generate an index.html for our application. html-webpack-plugin wires up the generated assets with it. Install it to the project:

npm i html-webpack-plugin --save-dev

Here is the configuration to setup the plugin and generate a bundle in our build directory:


const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');

const PATHS = {
  app: path.join(__dirname, 'app'),
  build: path.join(__dirname, 'build'),

module.exports = {
  // Entry accepts a path or an object of entries.
  // We'll be using the latter form given it's
  // convenient with more complex configurations.
  // Entries have to resolve to files! It relies on Node.js
  // convention by default so if a directory contains *index.js*,
  // it will resolve to that.
  entry: {
  output: {
    filename: '[name].js',
  plugins: [
    new HtmlWebpackPlugin({
      title: 'Webpack demo',

The entry path could be given as a relative one. The context field can be used to configure that lookup. Given plenty of places expect absolute paths, I prefer to use absolute paths everywhere to avoid confusion and keep it simple.

I use trailing commas in the book examples on purpose as it gives cleaner diffs for the code examples. I will show you how to enforce this rule in the Linting JavaScript chapter.
[name] is a placeholder. Placeholders are discussed in greater detail in the Adding Hashes to Filenames chapter.
I like to use path.join, but path.resolve would be a good alternative. See the Node.js path API for further details.

If you execute node_modules/.bin/webpack, you should see output:

Hash: d9b3a26d51481993359e
Version: webpack 2.2.0
Time: 375ms
     Asset       Size  Chunks             Chunk Names
    app.js    3.12 kB       0  [emitted]  app
index.html  180 bytes          [emitted]
   [0] ./app/component.js 135 bytes {0} [built]
   [1] ./app/index.js 77 bytes {0} [built]
Child html-webpack-plugin for "index.html":
       [0] ./~/lodash/lodash.js 540 kB {0} [built]
       [1] (webpack)/buildin/global.js 509 bytes {0} [built]
       [2] (webpack)/buildin/module.js 517 bytes {0} [built]
       [3] ./~/html-webpack-plugin/lib/loader.js!./~/html-webpack-plugin/default_index.ejs 540 bytes {0} [built]

The output tells us a lot. I've annotated it below:

  • Hash: d9b3a26d51481993359e - The hash of the build. You can use this to invalidate assets through [hash] placeholder. We'll discuss hashing in detail in the Adding Hashes to Filenames chapter.
  • Version: webpack 2.2.0 - Webpack version.
  • Time: 375ms - Time it took to execute the build.
  • app.js 3.12 kB 0 [emitted] app - Name of the generated asset, size, the ids of the chunks into which it is related, status information telling how it was generated, name of the chunk.
  • index.html 180 bytes [emitted] - Another generated asset that was emitted by the process.
  • [0] ./app/component.js 135 bytes {0} [built] - The id of the entry asset, name, size, entry chunk id, the way it was generated.
  • Child html-webpack-plugin for "index.html": - This is plugin-related output. In this case html-webpack-plugin is doing output of its own.

Examine the output below build/. If you look closely, you can see the same ids within the source. To see the application running, open the build/index.html file directly through a browser. On macOS open ./build/index.html works.

It can be convenient to use a tool like serve (npm i serve -g) to serve the build directory. In this case, execute serve at the output directory and head to localhost:3000 at your browser. You can configure the port through the --port parameter.

Adding a Build Shortcut#

Given executing node_modules/.bin/webpack is a little verbose, we should do something about it. npm and package.json double as a task runner with some configuration. Adjust it as follows:


"scripts": {
  "build": "webpack"

Run npm run build. You should see the same output as before.

This works because npm adds node_modules/.bin temporarily to the path. As a result, rather than having to write "build": "node_modules/.bin/webpack", we can do just "build": "webpack".

You can execute these kind of scripts through npm run. If you run it as is, it will give you the listing of available scripts.

There are shortcuts like npm start and npm test. We can run these directly without npm run although that will work too. For those in hurry, you can use npm t to run your tests.
It is possible to execute npm run anywhere within the project. It doesn't have to be run in the project root in order to work. npm will figure out the project root for you.

Useful Development Plugins#

As webpack plugin ecosystem is quite diverse, there are a lot of plugins that can help specifically with development. I've listed a few of these below to give you a better idea of what's available:

  • case-sensitive-paths-webpack-plugin has been designed to avoid issues with mixed path naming. A path that is valid on macOS might not be on Windows. If you work in a mixed environment, this plugin can be handy.
  • npm-install-webpack-plugin allows webpack to install and wire the installed packages with your package.json as you import new packages to your project. It's almost magical this way.
  • system-bell-webpack-plugin rings the system bell on failure instead of letting webpack fail silently.
  • friendly-errors-webpack-plugin improves on error reporting of webpack. It captures common errors and displays them in a friendlier manner, hence the name.
  • nyan-progress-webpack-plugin can be used to get tidier output during the build process. Take care with Continuous Integration (CI) systems like Travis, though, as they might clobber the output. Webpack provides webpack.ProgressPlugin for the same purpose. No nyan there, though.
  • webpack-dashboard gives an entire terminal based dashboard over the standard webpack output. If you prefer clear visual output, this one will come in handy.

In addition to plugins like these, it can be worth your while to set up linting to enforce coding standards. The Linting chapter digs into that topic in greater detail.

Useful html-webpack-plugin Extensions#

html-webpack-template or html-webpack-template-pug complement html-webpack-plugin and provide more powerful templates to use with it.

There are also specific plugins that extend html-webpack-plugin's functionality. I've listed a few of these below:


Even though we've managed to get webpack up and running, it's not that much yet. Developing against it would be painful. Each time we wanted to check out our application, we would have to build it manually using npm run build and then refresh the browser. That's where webpack's more advanced features come in and we'll look into enabling automatic browser refresh in the next chapter.

This book is available through Leanpub. By purchasing the book you support the development of further content. A part of profit (~30%) goes to Tobias Koppers, the author of Webpack.

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