webpack

What is webpack?

Webpack is a powerful module bundler for JavaScript applications. It processes applications by internally building a dependency graph which maps every module your project needs and generates one or more bundles. It is highly extensible via loaders and plugins, and it's designed to manage, transform, and bundle frontend assets like JavaScript, CSS, and images.

What are webpack's main functionalities?

Module Bundling

Webpack bundles all the JavaScript files and other assets like CSS and images into a single output file. The code sample shows a basic webpack configuration defining an entry point and the output bundle.

module.exports = {
  entry: './path/to/my/entry/file.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'my-first-webpack.bundle.js'
  }
};

Loaders

Loaders allow webpack to process different types of files and convert them into modules that can be included in your bundle. The code sample demonstrates how to use loaders to handle .txt and .css files.

module.exports = {
  module: {
    rules: [
      { test: /\.txt$/, use: 'raw-loader' },
      { test: /\.css$/, use: ['style-loader', 'css-loader'] }
    ]
  }
};

Plugins

Plugins can be leveraged to perform a wider range of tasks like bundle optimization, asset management, and environment variable injection. The code sample shows how to use the HtmlWebpackPlugin to generate an index.html file with the bundled assets injected.

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

module.exports = {
  plugins: [new HtmlWebpackPlugin({ template: './src/index.html' })]
};

Development Server

Webpack provides a development server that can be used to serve your application during development. It supports live reloading. The code sample configures the webpack development server to serve files from the 'dist' directory.

module.exports = {
  devServer: {
    contentBase: './dist',
    open: true
  }
};

Code Splitting

Code splitting allows you to split your code into various bundles which can then be loaded on demand or in parallel. The code sample shows how to split the application and vendor code into separate bundles.

module.exports = {
  entry: {
    app: './src/app.js',
    vendor: './src/vendor.js'
  },
  output: {
    filename: '[name].bundle.js',
    path: __dirname + '/dist'
  }
};

Other packages similar to webpack

rollup

Rollup is a module bundler for JavaScript which uses a flat bundle approach that's more efficient for libraries and applications with a complex module structure. It's known for its tree-shaking capabilities, which eliminate unused code.

parcel

Parcel is a web application bundler that offers a zero-configuration setup. It's known for its fast bundle times and out-of-the-box support for many file types without the need for additional plugins or loaders.

browserify

Browserify lets you require('modules') in the browser by bundling up all of your dependencies. It's been around longer than webpack and has a simpler approach, but it lacks some of the more advanced features and optimizations that webpack offers.

fuse-box

FuseBox is a bundler/module loader that combines the power of webpack, JSPM, and SystemJS. It introduces a streamlined workflow and has a powerful API. It's known for its speed and simplicity.

README

build

dependencies

donation

documentation

Introduction

webpack is a bundler for modules. The main purpose is to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset.

TL; DR

• Bundles both CommonJs and AMD modules (even combined).
• Can create a single bundle or multiple chunks that are asynchronously loaded at runtime (to reduce initial loading time).
• Dependencies are resolved during compilation reducing the runtime size.
• Loaders can preprocess files while compiling, e.g. coffeescript to JavaScript, handlebars strings to compiled functions, images to Base64, etc.
• Highly modular plugin system to do whatever else your application requires.

Getting Started

Check out webpack's documentation for quick Getting Started guide, in-depth usage, tutorials and resources.

Installation

project: npm install webpack --save-dev

global: npm install webpack -g Usage https://webpack.github.io/docs/tutorials/getting-started/

Examples

Take a look at the examples folder.

Features

Plugins

webpack has a rich plugin interface. Most of the features within webpack itself use this plugin interface. This makes webpack very flexible.

Performance

webpack uses async I/O and has multiple caching levels. This makes webpack fast and incredibly fast on incremental compilations.

Loaders

webpack enables use of loaders to preprocess files. This allows you to bundle any static resource way beyond JavaScript. You can easily write your own loaders using node.js.

Loaders are activated by using loadername! prefixes in require() statements, or are automatically applied via regex from your webpack configuration.

Please see Using Loaders for more information.

basic

• json: Loads file as JSON
• raw: Loads raw content of a file (as utf-8)
• val: Executes code as module and consider exports as JavaScript code
• script: Executes a JavaScript file once in global context (like in script tag), requires are not parsed.

packaging

• file: Emits the file into the output folder and returns the (relative) url.
• url: The url loader works like the file loader, but can return a Data Url if the file is smaller than a limit.
• image: Compresses your images. Ideal to use together with file or url.
• svgo-loader: Compresses SVG images using svgo library
• baggage: Automatically require any resources related to the required one
• polymer-loader: Process HTML & CSS with preprocessor of choice and require() Web Components like first-class modules.

dialects

• coffee: Loads coffee-script like JavaScript
• babel: Turn ES6 code into vanilla ES5 using Babel.
• livescript: Loads LiveScript like JavaScript
• sweetjs: Use sweetjs macros.
• traceur: Use future JavaScript features with Traceur.
• typescript: Loads TypeScript like JavaScript.

templating

• html: Exports HTML as string, require references to static resources.
• jade: Loads jade template and returns a function
• handlebars: Loads handlebars template and returns a function
• ractive: Pre-compiles Ractive templates for interactive DOM manipulation
• markdown: Compiles Markdown to HTML
• ng-cache: Puts HTML partials in the Angular's $templateCache

styling

• style: Add exports of a module as style to DOM
• css: Loads css file with resolved imports and returns css code
• cssnext: Loads and compiles a css file using cssnext
• less: Loads and compiles a less file
• sass: Loads and compiles a scss file
• stylus: Loads and compiles a stylus file

misc

• po: Loads a PO gettext file and returns JSON
• mocha: Do tests with mocha in browser or node.js
• eslint: PreLoader for linting code using ESLint.
• jshint: PreLoader for linting code.
• jscs: PreLoader for style checking.
• injectable: Allow to inject dependencies into modules
• transform: Use browserify transforms as loader.

For the full list of loaders, see list of loaders.

Module Format (AMD/CommonJS)

webpack supports both AMD and CommonJS module styles. It performs clever static analysis on the AST of your code. It even has an evaluation engine to evaluate simple expressions. This allows you to support most existing libraries out of the box.

Code Splitting

webpack allows you to split your codebase into multiple chunks. Chunks are loaded asynchronously at runtime. This reduces the initial loading time.

Code Splitting documentation

Optimizations

webpack can do many optimizations to reduce the output size of your JavaScript by deduplicating frequently used modules, minifying, and giving you full control of what is loaded initially and what is loaded at runtime through code splitting. It can also can make your code chunks cache friendly by using hashes.

Optimization documentation

webpack optimizes in several ways. It also makes your chunks cache-friendly by using hashes.

A small example of what's possible

// webpack is a module bundler.
// This means webpack takes modules with dependencies
// and emits static assets representing those modules.

// Dependencies can be written in CommonJs
var commonjs = require("./commonjs");
// or in AMD
define(["amd-module", "../file"], function (amdModule, file) {
	// while previous constructs are sync,
	// this is async
	require(["big-module/big/file"], function (big) {
		 // For async dependencies, webpack splits
		 // your application into multiple "chunks".
		 // This part of your application is
		 // loaded on demand (code-splitting).
		var stuff = require("../my/stuff");
		// "../my/stuff" is also loaded on-demand
		//  because it's in the callback function
		//  of the AMD require.
	});
});


require("coffee!./cup.coffee");
// "Loaders" are used to preprocess files.
// They can be prefixed in the require call
// or configured in the configuration.
require("./cup");
// This does the same when you add ".coffee" to the extensions
// and configure the "coffee" loader for /\.coffee$/

function loadTemplate (name) {
	return require("./templates/" + name + ".jade");
	// Many expressions are supported in require calls.
	// A clever parser extracts information and concludes
	// that everything in "./templates" that matches
	// /\.jade$/ should be included in the bundle, as it
	// can be required.
}


// ...and you can combine everything.
function loadTemplateAsync (name, callback) {
	require(["bundle?lazy!./templates/" + name + ".jade"],
	  function (templateBundle) {
	          templateBundle(callback);
	});
}

Documentation

documentation

Changelog

changelog

Tests

You can run the Node tests with npm test.

You can run the browser tests:

cd test/browsertests
node build

and open tests.html in the browser.

Contribution

Most of the time, if webpack is not working correctly for you it is a simple configuration issue.

If you are still having difficulty after looking over your configuration carefully, please post a question to StackOverflow with the webpack tag. Questions that include your webpack.config.js and relevant files are more likely to receive responses.

If you have discovered a bug or have a feature suggestion, feel free to create an issue on Github.

If you create a loader or plugin, please consider open sourcing it, putting it on NPM and following the x-loader, x-plugin convention.

You are also welcome to correct any spelling mistakes or any language issues.

If you want to discuss something or just need help, here is our gitter.im room.

License

Copyright (c) 2012-2015 Tobias Koppers

MIT (http://www.opensource.org/licenses/mit-license.php)

Thanks to

(In chronological order)

• @google for Google Web Toolkit (GWT), which aims to compile Java to JavaScript. It features a similar Code Splitting as webpack.
• @medikoo for modules-webmake, which is a similar project. webpack was born because I wanted Code Splitting for modules-webpack. Interestingly the Code Splitting issue is still open (thanks also to @Phoscur for the discussion).
• @substack for browserify, which is a similar project and source for many ideas.
• @jrburke for require.js, which is a similar project and source for many ideas.
• @defunctzombie for the browser-field spec, which makes modules available for node.js, browserify and webpack.
• Every early webpack user, which contributed to webpack by writing issues or PRs. You influenced the direction...
• @shama, @jhnns and @sokra for maintaining this project
• Everyone who has written a loader for webpack. You are the ecosystem...
• Everyone I forgot to mention here, but also influenced webpack.

Sponsor

This is a free-time project. The time I invest in it fluctuates. If you use webpack for a serious task, and you'd like me to invest more time on it, please donate. This project increases your income/productivity too. It makes development and applications faster and it reduces the required bandwidth.

I'm very thankful for every dollar. If you leave your username or email, I may show my thanks by giving you extra support.

Dependencies

• esprima
• enhanced-resolve
• uglify-js
• mocha
• should
• optimist
• async
• mkdirp
• clone