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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 similar to webpack keep a essential a part of the JavaScript toolchain. Let’s take a deep dive into what webpack is and how one can use it in your improvement workflow.

Within the early days when modularity was launched in JavaScript, there was no native assist for operating modules inside 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 purposes.

It additionally had prospects for giant net purposes 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 net browsers, the place JavaScript was normally executed.

To unravel this downside, module bundlers similar to webpack, Parcel, Rollup and in addition Google’s Closure Compiler had been written to create optimized bundles of your code to 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 might be understood higher as the tip product of all the bundling course of.

On this article, we can be specializing in webpack, a software written by Tobias Koppers, which over time has grown to develop into a serious software inside the JavaScript toolchain, usually utilized in giant and small tasks.

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

What Is webpack?

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

As proven within the illustration beneath, webpack goes by way of your software from a root entry level, builds a dependency graph comprising of dependencies that act straight or not directly on the basis 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 commonly used on this article, and it’s additionally regularly referenced in webpack’s documentation.

  • Chunk
    A chunk refers back to the code extracted from modules. This code can be saved in a chunk file. Chunks are generally used when performing code-splitting with webpack.
  • Modules
    Modules are broken-down elements of your software which you import to carry out a particular activity or perform. Webpack helps modules created utilizing the ES6, CommonJS and AMD syntax.
  • Belongings
    The time period property is regularly used inside webpack and different bundlers basically. It refers back to the static recordsdata bundled through the construct course of. These recordsdata could possibly be something from photos to fonts and even video recordsdata. As you learn additional down the article, you will note how we use loaders to work with totally different asset varieties.

Beneficial 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 undertaking.

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

webpack Configuration Information

Alternatively to utilizing the webpack-cli from a terminal, you should use webpack in your undertaking through a configuration file. However with the current variations of webpack, we will use webpack in our undertaking 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 manner, webpack will assume your undertaking’s entry level file lives within the src listing. It should 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 out a 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, far 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 software 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 will outline a customized entry and output file paths slightly than the default path utilized by webpack.

A couple of issues to notice a couple of 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 possibility:
    • mode
      In configuration, this feature is used to set the NODE_ENV worth throughout bundling. It will probably both have a manufacturing or improvement worth. When not specified, it’ll default to none. It’s additionally necessary to notice that webpack bundles your property in another way primarily based on the mode worth. For instance, webpack mechanically caches your bundles in improvement mode to optimize and cut back the bundle time. Discuss with the mode section of the webpack documentation to see a changelog of the choices mechanically utilized in every mode.

webpack Ideas

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

It’s value 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 straight or not directly on the entry level.

Your configuration’s entry level is usually a Single Entry kind with a single file worth, just like the instance beneath:

# webpack.configuration.js

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

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

# webpack.configuration.js

const webpack = require("webpack")

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

Output

Simply because the identify implies, a configuration’s output discipline is the place the created bundle will stay. This discipline is useful when you have got a number of modules in place. Reasonably than utilizing the identify generated by webpack, you possibly can specify your personal filename.

# webpack.configuration.js

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

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

Loaders

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

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

There are 3 ways to make use of loaders inside your software. One in every of them is thru the inline methodology by straight importing it within the file. For instance, to attenuate picture dimension, we will use the image-loader loader within the file straight as proven beneath:

// predominant.js

import ImageLoader from 'image-loader'

One other most popular possibility to make use of loaders is through your webpack configuration file. This manner, you are able to do extra with loaders, similar 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 take a look at discipline with a regex expression matching the property we need to apply the loaders to.

For examples, with image-loader imported straight within the earlier instance, we will use it within the webpack configuration file with essentially the most primary choices from the documentation. This can appear like this:

# webpack.config.js

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

module.exports = {
  mode: "improvement",
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  },
  module: {
    guidelines: [
    svg)$/i,
      use: [
        'img-loader'
        ]
    
   ]
  }
}

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

The final methodology of utilizing Loaders is through the CLI with the --module-bind flag.

The awesome-webpack readme comprises an exhaustive record of loaders that you should use with webpack, every grouped into classes of operations that they carry out. Beneath are just some loaders that you just would possibly discover helpful in your software:

  • Responsive-loader
    You’ll find this loader very useful when including photos to suit your responsive website or app. It creates a number of photos of assorted sizes from a single picture and returns a srcset matching the pictures to be used at applicable 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 hundreds your .graphql recordsdata containing your GraphQL schema, queries, and mutations — together with the choice to allow validation.

Plugins

The usage of plugins permits webpack compiler to carry out duties on chunks produced from the bundled modules. Though webpack is just not a activity runner, with plugins, we will 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 gives a option 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: "improvement",
  entry: './src/entry',
  output: {
    filename: "webpack-output.js",
    path: path.resolve(__dirname, "dist"),
  },
  module: {
    guidelines: [
    svg)$/i,
      use: [
        'img-loader'
        ]
    
   ]
  },
  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 perform that may print out the compilation proportion and message to the console through the compilation course of.

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

Beneath are just a few plugins from the awesome-webpack readme which you’ll discover helpful in your webpack software.

  • Offline-plugin
    This plugin makes use of service workers first or the AppCache the place accessible to supply an offline expertise for webpack managed tasks.
  • Purgecss-webpack-plugin
    This plugin is useful when attempting to optimize your webpack undertaking because it removes unused CSS inside your software throughout compilation.

At this level, we’ve got our first webpack configuration for a comparatively small software absolutely arrange. Let’s additional take into account how we will do sure issues with webpack in our software.

Dealing with A number of Environments

In your software, you would possibly have to configure webpack in another way for both a improvement or manufacturing setting. For instance, you may not need webpack to output minor warning logs every time a brand new deployment is made to your steady integration pipeline in your manufacturing setting.

There are several ways to attain that, as really helpful by webpack and the group. A technique is to convert your configuration file to export a perform that returns an object. This manner, present setting can be handed into the perform by the webpack compiler as its first parameter, and different possibility because the second parameter.

This methodology of dealing with your webpack setting will come in useful if there are just a few operations you’d prefer to carry out in another way primarily based on the present setting. Nonetheless, for bigger purposes with extra complicated configurations, you would find yourself with a configuration full of loads of conditional statements.

The code snippet beneath reveals an instance of how one can deal with a manufacturing and improvement setting in the identical file utilizing the capabilities methodology.

// webpack.config.js

module.exports = perform (env, args) {
  return {
   mode : env.manufacturing ? 'manufacturing' : 'improvement',
  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 by way of the exported perform within the code snippet above, you’ll see how the env parameter handed into the perform is getting used with a ternary operator to change values. It’s first used to set the webpack mode, then it’s additionally used to allow the ProgressPlugin solely in improvement mode.

One other extra elegant option to deal with your manufacturing and improvement setting is to create totally different configuration recordsdata for the 2 environments. As soon as we’ve performed that, we will 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 got two script instructions, every utilizing a distinct configuration file written to deal with a particular setting when bundling the applying’s property. Now you possibly can bundle your software utilizing npm run bundle:dev in improvement mode, or npm run bundle:prod when making a production-ready bundle.

Utilizing the second method, you keep away from conditional statements launched when returning your configuration object from a perform. Nonetheless, now you even have to keep up a number of configuration recordsdata.

Splitting Configuration File

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

For a bigger software 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 will cut up the configuration into smaller objects throughout a number of recordsdata then use the webpack-merge bundle to merge the configuration objects into one base file.

To use it to our webpack undertaking, we will cut up the only configuration file into three smaller recordsdata: one for loaders, one for plugins, and the final file as the bottom configuration file the place we put the 2 different recordsdata 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 got 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: [
    svg)$/i,
      use: [
        'img-loader'
        ]
    
  ]
  }
}

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 software can be stored alongside the 2 created recordsdata 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: "improvement",
  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 recordsdata and can be utilized individually.

Optimizing Massive Builds

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

By default, webpack mechanically tries to optimize bundles in your behalf in case your configuration mode is about to manufacturing. For instance, one approach 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 approach used to take away unused code. At a easy degree throughout bundling, the import and export statements are used to detect unused modules earlier than eradicating them from the emitted bundles.

It’s also possible to manually optimize your software bundle by including an optimization object with sure fields into your configuration file. The optimization section of the webpack documentation comprises a full record of fields you should use within the optimization object to, properly, optimize your software. Let’s take into account 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 popular minifiers by including a minimizer array discipline inside the optimization object. An instance is using 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 necessary choices. First, enabling cache signifies that Uglify will solely minify present recordsdata when they’re new modifications, and the take a look at possibility specifies the precise file varieties we need to minify.

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

A Little Optimization Demo

Let’s manually attempt to optimize a demo software by making use of some fields in a bigger undertaking 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 improvement mode, versus when in manufacturing mode.

For this demo, we’ll use a desktop software 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 fairly heavy mixture and would possibly doubtless generate an even bigger bundle.

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

To check out the demo regionally, 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 software is pretty easy with a single web page styled utilizing styled-components. When the desktop software is launched with the yarn begin command, the only web page shows a listing of photos fetched from a CDN, as proven beneath.

Electron application with React.js interface preview.
Desktop preview of photos inside the Electron software with React.js interface. (Large preview)

Let’s create a improvement bundle of this software first with none handbook optimization to investigate the ultimate bundle dimension.

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

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

The command will present us the statistics of all the 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 software.

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 info beneath to your terminal.

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

Take a observe 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 comprise 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 displaying a visible illustration of emitted bundle and recordsdata inside. (Large preview)

From the picture above, we will see a visible illustration of the emitted bundle and file sizes inside the bundle. Within the visible, we will 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 concept of what put in bundle is contributing the most important portion of the bundle. We are able to then search for methods to optimize it or substitute it with a lighter bundle.

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

One of many strengths of webpack has been the giant group of builders behind it and this has been of nice use to builders attempting 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 an excellent information when utilizing webpack.

For instance, Build Performance guide from webpack’s blog comprises recommendations on 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 tasks to point out 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 characteristic is utilized in a React software.

Abstract

After seven years of its existence, webpack has actually proved itself to be an necessary a part of the JavaScript toolchain utilized by a lot of tasks. 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 to your software, hopefully you’ll higher perceive some core ideas of Webpack, the issue it solves, and in addition the steps of organising your configuration recordsdata.

Additional Studying on SmashingMag:

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