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Friday June 4, 2021 By David Quintanilla
Getting Started With Webpack — Smashing Magazine


About The Creator

Nwani Victory works remotely as a Fullstack developer from Lagos, Nigeria. After workplace hours, he doubles as a Cloud Engineer looking for methods to make Cloud …
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Fashionable browsers present good support for JavaScript modules, however module bundlers comparable to webpack keep a vital a part of the JavaScript toolchain. Let’s take a deep dive into what webpack is and methods to use it in your growth workflow.

Within the early days when modularity was launched in JavaScript, there was no native assist for operating modules throughout the browser. Help for modular programming was being carried out in Node.js utilizing the CommonJS blueprint and it was being adopted by these utilizing JavaScript for constructing server-side functions.

It additionally had prospects for massive internet functions as builders might keep away from namespace collisions and construct extra maintainable codebases by writing code in a extra modular sample. However there was nonetheless a problem: modules couldn’t be used inside internet browsers, the place JavaScript was normally executed.

To resolve this drawback, module bundlers comparable to webpack, Parcel, Rollup and in addition Google’s Closure Compiler have been written to create optimized bundles of your code on your end-user’s browser to obtain and execute.

What Does It Imply To “Bundle” Your Code?

Bundling code refers to combining and optimizing a number of modules into a number of production-ready bundles. The bundle talked about right here will be understood higher as the top product of the whole bundling course of.

On this article, we will probably be specializing in webpack, a software written by Tobias Koppers, which over time has grown to turn out to be a serious software throughout the JavaScript toolchain, typically utilized in massive and small initiatives.

Be aware: To learn from this text, it’s a good suggestion to be aware of JavaScript modules. Additionally, you will want Node put in in your native machine, so you possibly can set up and use webpack domestically.

What Is webpack?

webpack is a extremely extensible and configurable static module bundler for JavaScript functions. With its extensible nature, you possibly can plug in exterior loaders and plugins to realize your finish objective.

As proven within the illustration beneath, webpack goes via your utility from a root entry level, builds a dependency graph comprising of dependencies that act instantly or not directly on the foundation file and produces optimized bundles of the mixed modules.

webpack depedency graph illustration
An illustration of depedency graph graph generated by webpack ranging from an entry level. (Large preview)

To know how webpack works, we have to perceive some terminology that it makes use of (examine webpack Glossary. This terminology is usually used on this article, and it’s additionally ceaselessly referenced in webpack’s documentation.

  • Chunk
    A chunk refers back to the code extracted from modules. This code will probably be saved in a chunk file. Chunks are generally used when performing code-splitting with webpack.
  • Modules
    Modules are broken-down elements of your utility which you import to carry out a particular job or operate. Webpack helps modules created utilizing the ES6, CommonJS and AMD syntax.
  • Belongings
    The time period property is ceaselessly used inside webpack and different bundlers on the whole. It refers back to the static information bundled through the construct course of. These information may very well be something from photographs to fonts and even video information. As you learn additional down the article, you will note how we use loaders to work with totally different asset varieties.

Really helpful studying: Webpack – A Detailed Introduction

As soon as we’ve understood what webpack is and what terminology it makes use of, let’s see how they apply in placing collectively a configuration file for a demo mission.

Be aware: Additionally, you will want webpack-cli put in to make use of webpack in your machine. If not put in, you can be prompted out of your terminal to put in it.

webpack Configuration Recordsdata

Alternatively to utilizing the webpack-cli from a terminal, you need to use webpack in your mission by way of a configuration file. However with the current variations of webpack, we are able to use webpack in our mission with out a configuration file. We then use webpack as a worth of one of many instructions in our bundle.json file, with none flag. This fashion, webpack will assume your mission’s entry level file lives within the src listing. It can bundle the entry file and output it to the dist listing.

An instance is a pattern bundle.json file beneath. We use webpack to bundle the applying with no configuration file:

{
  "identify" : "Smashing Journal",
  "predominant": "index.js",
  "scripts": {
      "construct" : "webpack"
  },
  "dependencies" : {
    "webpack": "^5.24.1"
  }
}

When operating it the construct command within the file above, webpack will bundle the file within the src/index.js listing and output it in a predominant.js file in a dist listing. webpack is, nonetheless, way more versatile than that. We are able to change the entry level, modify the output level and refine many different default behaviors by modifying a configuration file with the -- config flag.

An instance is the modified construct command from the bundle.json file above:

"construct" : "webpack --config webpack.config.js"

Above, we added the --config flag and specified a webpack.config.js because the file having the brand new webpack configuration.

The webpack.config.js file doesn’t exist but although. So we have to create it in our utility listing and paste the next code beneath into the file.

# webpack.config.js

const path = require("path")

module.exports = {
  entry : "./src/entry",
  output : {
    path: path.resolve(__dirname, "dist"),
    filename: "output.js"
  }
}

The file above nonetheless configures webpack to bundle your JavaScript file, however now we are able to outline a customized entry and output file paths somewhat than the default path utilized by webpack.

A couple of issues to notice a few webpack configuration file:

  • A webpack configuration file is a JavaScript file, written as a JavaScript CommonJS module.
  • A webpack configuration file exports an object with a number of properties. Every of those properties is used as an choice to configure webpack when bundling your code. An instance is the mode choice:
    • mode
      In configuration, this feature is used to set the NODE_ENV worth throughout bundling. It could both have a manufacturing or growth worth. When not specified, it can default to none. It’s additionally essential to notice that webpack bundles your property in another way based mostly on the mode worth. For instance, webpack routinely caches your bundles in growth mode to optimize and cut back the bundle time. Consult with the mode section of the webpack documentation to see a changelog of the choices routinely utilized in every mode.

webpack Ideas

When configuring webpack both by way of the CLI or via a configuration file, there are 4 predominant ideas which can be utilized as choices. The following part of this text focuses on these ideas and applies them when constructing the configuration for a demo internet utility.

It’s price noting that the ideas defined beneath share some similarities with different module bundlers. For instance, when utilizing Rollup with a configuration file, you possibly can outline an input discipline to specify the entry level of the dependency graph, an output object configuring how and the place the produced chunks are positioned, and in addition a plugins object for including exterior plugins.

Entry

The entry discipline in your configuration file comprises the trail to the file from the place webpack begins constructing a dependency graph. From this entry file, webpack will proceed to different modules which rely instantly or not directly on the entry level.

Your configuration’s entry level could be a Single Entry kind with a single file worth, much like the instance beneath:

# webpack.configuration.js

module.exports = {
  mode:  "growth",
  entry : "./src/entry" 
}

The entry level will also be a multi-main entry kind having an array containing the trail to a number of entry information, much like the instance beneath:

# webpack.configuration.js

const webpack = require("webpack")

module.exports = {
  mode: "growth",
  entry: [ './src/entry', './src/entry2' ],
}

Output

Simply because the identify implies, a configuration’s output discipline is the place the created bundle will reside. This discipline turns out to be useful when you might have a number of modules in place. Relatively than utilizing the identify generated by webpack, you possibly can specify your individual filename.

# webpack.configuration.js

const webpack = require("webpack");
const path = require("path");

module.exports = {
  mode: "growth",
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  }
}

Loaders

By default, webpack solely understands JavaScript information inside your utility. Nonetheless, webpack treats each file imported as a module as a dependency, and provides it to the dependency graph. To course of static sources comparable to photographs, CSS information, JSON information and even your knowledge saved in CSV, webpack makes use of loaders to “load” these information into the bundle.

Loaders are versatile sufficient for use for lots of issues, from transpiling your ES code, to dealing with your utility’s types and even linting your code with ESLint.

There are 3 ways to make use of loaders inside your utility. One in all them is thru the inline technique by instantly importing it within the file. For instance, to attenuate picture dimension, we are able to use the image-loader loader within the file instantly as proven beneath:

// predominant.js

import ImageLoader from 'image-loader'

One other most well-liked choice to make use of loaders is by way of your webpack configuration file. This fashion, you are able to do extra with loaders, comparable to specifying the file varieties you need to apply the loaders to. To do that, we create a guidelines array and specify the loaders in an object, every having a check discipline with a regex expression matching the property we need to apply the loaders to.

For examples, with image-loader imported instantly within the earlier instance, we are able to use it within the webpack configuration file with essentially the most primary choices from the documentation. It will appear like this:

# webpack.config.js

const webpack = require("webpack")
const path = require("path")
const merge = require("webpack-merge")

module.exports = {
  mode: "growth",
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  },
  module: {
    guidelines: [
    gif
   ]
  }
}

Take a more in-depth have a look at the check discipline within the object that comprises the image-loader above. We are able to spot the regex expression that matches all picture information: both jp(e)g, png, gif and svg format.

The final technique of utilizing Loaders is by way of the CLI with the --module-bind flag.

The awesome-webpack readme comprises an exhaustive listing of loaders that you need to use with webpack, every grouped into classes of operations that they carry out. Beneath are only a few loaders that you just may discover helpful in your utility:

  • Responsive-loader
    You’ll find this loader very useful when including photographs to suit your responsive website or app. It creates a number of photographs of varied sizes from a single picture and returns a srcset matching the photographs to be used at acceptable show display screen sizes.
  • Babel-loader
    That is used for transpiling your JavaScript code from trendy ECMA syntax to ES5.
  • GraphQL-Loader
    If you’re a GraphQL fanatic, you’ll discover this loader fairly useful because it masses your .graphql information containing your GraphQL schema, queries, and mutations — together with the choice to allow validation.

Plugins

Using plugins permits webpack compiler to carry out duties on chunks produced from the bundled modules. Though webpack will not be a job runner, with plugins, we are able to carry out some customized actions which the loaders couldn’t carry out when the code was being bundled.

An instance of a webpack plugin is the ProgressPlugin built-in to webpack. It offers a technique to customise the progress which is printed out within the console throughout compilation.

# webpack.config.js

const webpack = require("webpack")
const path = require("path")
const merge = require("webpack-merge")

const config = {
  mode: "growth",
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  },
  module: {
    guidelines: [
    gif
   ]
  },
  plugins: [ 
        new webpack.ProgressPlugin({
          handler: (percentage, message ) => {
            console.info(percentage, message);
          },
        })
    ]
}

module.exports = config

With the Progress plugin within the configuration above, we offered a handler operate that can print out the compilation share and message to the console through the compilation course of.

webpack progress plugin output
A shell output exhibiting messages from webpack progress plugin. (Large preview)

Beneath are a couple of plugins from the awesome-webpack readme which you will see helpful in your webpack utility.

  • Offline-plugin
    This plugin makes use of service workers first or the AppCache the place out there to supply an offline expertise for webpack managed initiatives.
  • Purgecss-webpack-plugin
    This plugin turns out to be useful when making an attempt to optimize your webpack mission because it removes unused CSS inside your utility throughout compilation.

At this level, we’ve our first webpack configuration for a comparatively small utility absolutely arrange. Let’s additional think about how we are able to do sure issues with webpack in our utility.

Dealing with A number of Environments

In your utility, you may have to configure webpack in another way for both a growth or manufacturing surroundings. For instance, you won’t need webpack to output minor warning logs every time a brand new deployment is made to your steady integration pipeline in your manufacturing surroundings.

There are several ways to realize that, as beneficial by webpack and the group. A technique is to convert your configuration file to export a operate that returns an object. This fashion, present surroundings will probably be handed into the operate by the webpack compiler as its first parameter, and different choice because the second parameter.

This technique of dealing with your webpack surroundings will turn out to be useful if there are a couple of operations you’d wish to carry out in another way based mostly on the present surroundings. Nonetheless, for bigger functions with extra advanced configurations, you may find yourself with a configuration filled with loads of conditional statements.

The code snippet beneath reveals an instance of methods to deal with a manufacturing and growth surroundings in the identical file utilizing the features technique.

// webpack.config.js

module.exports = operate (env, args) {
  return {
   mode : env.manufacturing ? 'manufacturing' : 'growth',
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  },
  plugins: [ 
       env.development && ( 
          new webpack.ProgressPlugin({
            handler: (percentage, message ) => {
                console.info(percentage, message);
            },
        })
      )
    ]
  }
}

Going via the exported operate within the code snippet above, you’ll see how the env parameter handed into the operate is getting used with a ternary operator to modify values. It’s first used to set the webpack mode, then it’s additionally used to allow the ProgressPlugin solely in growth mode.

One other extra elegant technique to deal with your manufacturing and growth surroundings is to create totally different configuration information for the 2 environments. As soon as we’ve accomplished that, we are able to use them with totally different instructions within the bundle.json scripts when bundling the applying. Check out the snippet beneath:

{
  "identify" : "smashing-magazine", 
  "predominant" : "index.js"
  "scripts" : {
    "bundle:dev" : "webpack --config webpack.dev.config.js",
    "bundle:prod" : "webpack --config webpack.prod.config.js"
  },
  "dependencies" : {
    "webpack": "^5.24.1"
  }
}

Within the bundle.json above, we’ve two script instructions, every utilizing a unique configuration file written to deal with a particular surroundings when bundling the applying’s property. Now you possibly can bundle your utility utilizing npm run bundle:dev in growth mode, or npm run bundle:prod when making a production-ready bundle.

Utilizing the second strategy, you keep away from conditional statements launched when returning your configuration object from a operate. Nonetheless, now you even have to take care of a number of configuration information.

Splitting Configuration File

At this level, our webpack configuration file is at 38 traces of code (LOC). That is fairly positive for a demo utility with a single loader and a single plugin.

For a bigger utility although, our webpack configuration file will certainly be a lot longer, having a number of loaders and plugins with their customized choices every. To maintain the configuration file clear and readable, we are able to cut up the configuration into smaller objects throughout a number of information then use the webpack-merge bundle to merge the configuration objects into one base file.

To use it to our webpack mission, we are able to cut up the one configuration file into three smaller information: one for loaders, one for plugins, and the final file as the bottom configuration file the place we put the 2 different information collectively.

Create a webpack.plugin.config.js file and paste the code beneath into it to make use of the plugins with further choices.

// webpack.plugin.config.js
const webpack = require('webpack')
 
const plugin = [
  new webpack.ProgressPlugin({
          handler: (percentage, message ) => {
            console.info(percentage, message);
          },
  })
]

module.exports = plugin

Above, we’ve a single plugin which we extracted from the webpack.configuration.js file.

Subsequent, create a webpack.loader.config.js file with the code beneath for the webpack loaders.

// webpack.loader.config.js

const loader = {
 module: {
    guidelines: [
    gif
  ]
  }
}

Within the code block above, we moved the webpack img-loader right into a separate file.

Lastly, create a webpack.base.config.js file the place the bottom enter and output configuration for the webpack utility will probably be saved alongside the 2 created information above.

// webpack.base.config.js
const path = require("path")
const merge = require("webpack-merge")

const plugins = require('./webpack.plugin.config')
const loaders = require('./webpack.loader.config')

const config = merge(loaders, plugins, {
  mode: "growth",
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  }
});

module.exports = config

Taking a look on the webpack file above, you possibly can observe how compact it’s compared to the unique webpack.config.js file. Now the three predominant elements of the configuration have been damaged into smaller information and can be utilized individually.

Optimizing Massive Builds

As you retain working in your utility over a time period, your utility will certainly develop bigger in options and dimension. As this occurs, new information will probably be created, outdated information will probably be modified or refactored, and new exterior packages will probably be put in — all resulting in an improve within the bundle dimension emitted by webpack.

By default, webpack routinely tries to optimize bundles in your behalf in case your configuration mode is about to manufacturing. For instance, one method that webpack applies by default (beginning with webpack 4+) to optimize and cut back your bundle dimension is Tree-Shaking. Basically, it’s an optimization method used to take away unused code. At a easy stage throughout bundling, the import and export statements are used to detect unused modules earlier than eradicating them from the emitted bundles.

You can even manually optimize your utility bundle by including an optimization object with sure fields into your configuration file. The optimization section of the webpack documentation comprises a full listing of fields you need to use within the optimization object to, properly, optimize your utility. Let’s think about one out of the 20 documented fields.

  • decrease
    This boolean discipline is used to instruct webpack to attenuate the bundle dimension. By default, webpack will attempt to obtain this utilizing TerserPlugin, a code minification bundle shipped with webpack.

“Minification applies to minimizing your code by eradicating pointless knowledge from the code which in flip reduces the code dimension produced after the method.”

We are able to additionally use different most well-liked minifiers by including a minimizer array discipline throughout the optimization object. An instance is the usage of Uglifyjs-webpack-plugin beneath.

// webpack.config.js
const Uglify = require("uglifyjs-webpack-plugin")

module.exports = {
    optimization {
      decrease : true,
      minimizer : [
        new Uglify({
          cache : true,
          test: /.js(?.*)?$/i,
       })
    ]
  } 
 }

Above, uglifyjs-webpack-plugin is getting used as a minifier with two fairly essential choices. First, enabling cache implies that Uglify will solely minify current information when they’re new modifications, and the check choice specifies the particular file varieties we need to minify.

Be aware: The uglifyjs-webpack-plugin offers a complete listing of the choices out there to be used when minifying your code with it.

A Little Optimization Demo

Let’s manually attempt to optimize a demo utility by making use of some fields in a bigger mission to see the distinction. Though we gained’t dive deep into optimizing the applying, we’ll see the distinction in bundle sizes between when operating webpack in growth mode, versus when in manufacturing mode.

For this demo, we’ll use a desktop utility constructed with Electron that additionally makes use of React.js for its UI — all bundled along with webpack. Electron and React.js sound like a reasonably heavy mixture and may possible generate a much bigger bundle.

Be aware: If you’re studying about Electron for the primary time, this article offers a very good perception into what Electron is and the way you need to use it for constructing cross-platform desktop functions.

To check out the demo domestically, clone the applying from the GitHub repository and set up the dependencies utilizing the instructions beneath.

# clone repository
git clone https://github.com/vickywane/webpack-react-demo.git

# change listing
cd demo-electron-react-webpack

# set up dependencies
npm set up

The desktop utility is pretty easy with a single web page styled utilizing styled-components. When the desktop utility is launched with the yarn begin command, the one web page shows a listing of photographs fetched from a CDN, as proven beneath.

Electron application with React.js interface preview.
Desktop preview of photographs throughout the Electron utility with React.js interface. (Large preview)

Let’s create a growth bundle of this utility first with none guide optimization to investigate the ultimate bundle dimension.

Working yarn construct:dev from a terminal within the mission listing will create the event bundle. Plus, it can print out the next statistics to your terminal:

webpack compiler logs in development mode
Terminal logs from webpack compiler when run in growth mode with out guide optimizations. (Large preview)

The command will present us the statistics of the whole compilation and the emitted bundles.

Pay attention to the mainRenderer.js chunk is at 1.11 Mebibyte (approx 1.16 MB). The mainRenderer is the entry level for the Electron utility.

Subsequent, let’s add uglifyjs-webpack-plugin as an put in plugin within the webpack.base.config.js file for code minification.

// webpack.base.config.js
const Uglifyjs = require("uglifyjs-webpack-plugin")

module.exports = {
  plugins : [
    new Uglifyjs({
      cache : true
    })
  ]
}

Lastly, let’s run bundle the applying with webpack in manufacturing mode. Working yarn construct:prod command out of your terminal will output the information beneath to your terminal.

webpack compiler logs in production mode.
Logs from webpack compiler when utility is bundled in manufacturing mode with code minification. (Large preview)

Take a be aware of the mainRenderer chunk this time. It has dropped to a whopping 182 Kibibytes (roughly 186 KB), and that’s greater than 80% of the mainRenderer chunk dimension emitted beforehand!

Let’s additional visualize the emitted bundles utilizing the webpack-bundler-analyzer. Set up the plugin utilizing the yarn add webpack-bundle-analyzer command and modify the webpack.base.config.js file to include the code beneath which provides the plugin.

// webpack.base.config.js
const Uglifyjs = require("uglifyjs-webpack-plugin");
const BundleAnalyzerPlugin = require("webpack-bundle-analyzer");
  .BundleAnalyzerPlugin;

const config = {
  plugins: [
    new Uglifyjs({
      cache : true
    }),
    new BundleAnalyzerPlugin(),
  ]
};

module.exports = config;

Run yarn construct:prod out of your terminal for the applying to be re-bundled. By default, webpack-bundle-analyzer will begin an HTTP server that serves the visualized overview of the bundles in your browser.

Bundle analyzer representation of emitted bundle.
webpack bundle analyzer exhibiting a visible illustration of emitted bundle and information inside. (Large preview)

From the picture above, we are able to see a visible illustration of the emitted bundle and file sizes throughout the bundle. Within the visible, we are able to observe that within the folder node_modules, the most important file is the react-dom.manufacturing.min.js, adopted by stylis.min.js.

Utilizing the file sizes visualized by the analyzer, we’ll have a greater thought of what put in bundle is contributing the key portion of the bundle. We are able to then search for methods to optimize it or change it with a lighter bundle.

Be aware: The webpack-analyzer-plugin documentation lists different means out there for displaying the evaluation created out of your emitted bundles.

One of many strengths of webpack has been the massive group of builders behind it and this has been of nice use to builders making an attempt webpack out for the primary time. Identical to this text, there are a number of articles, guides and sources with the documentation that serves as a fantastic information when utilizing webpack.

For instance, Build Performance guide from webpack’s blog comprises tips about optimizing your webpack builds and Slack’s case study (though a bit outdated) explains how webpack was optimized at Slack.

A number of group sources clarify elements of webpack’s documentation, offering you with pattern demo initiatives to indicate how options of webpack are getting used. An instance is an article on Webpack 5 Module Federation which explains how webpack’s new Module Federation function is utilized in a React utility.

Abstract

After seven years of its existence, webpack has really proved itself to be an essential a part of the JavaScript toolchain utilized by numerous initiatives. This text solely offers a glimpse into the issues one can obtain with webpack’s versatile and extensible nature.

The following time it is advisable to select a module bundler on your utility, hopefully you’ll higher perceive some core ideas of Webpack, the issue it solves, and in addition the steps of organising your configuration information.

Additional Studying on SmashingMag:

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