مقدمة إلى Webpack

Webpack هي أداة حظيت باهتمام كبير في السنوات القليلة الماضية ، وهي تُستخدم الآن في كل مشروع تقريبًا. تعرف عليها.

ما هو webpack؟

Webpack هي أداة تتيح لك تجميع وحدات JavaScript النمطية ، والمعروفة أيضًا باسموحدة التجميع.

نظرًا لوجود عدد كبير من الملفات ، فإنه ينشئ ملفًا واحدًا (أو بعض الملفات) يقوم بتشغيل تطبيقك.

يمكنه إجراء العديد من العمليات:

  • يساعدك في تجميع مواردك.
  • يراقب التغييرات ويعيد تشغيل المهام.
  • يمكن تشغيل Babel transpilation إلى ES5 ، مما يتيح لك استخدام الأحدثJavaScriptالميزات دون القلق بشأن دعم المتصفح.
  • يمكن تحويل CoffeeScript إلى JavaScript
  • يمكن تحويل الصور المضمنة إلى عناوين URL للبيانات.
  • يسمح لك باستخدام يتطلب () لملفات CSS.
  • يمكن تشغيل خادم ويب تطوير.
  • يمكن التعامل مع استبدال الوحدة الساخنة.
  • يمكن تقسيم ملفات الإخراج إلى ملفات متعددة ، لتجنب وجود ملف js ضخم للتحميل في أول صفحة.
  • يستطيع اداءتهز الشجرة.

لا يقتصر استخدام Webpack على الواجهة الأمامية ، بل إنه مفيد أيضًا في تطوير الواجهة الخلفية Node.js.

تشمل أسلاف حزمة الويب ، والأدوات التي لا تزال مستخدمة على نطاق واسع ، ما يلي:

  • الناخر
  • بروكلي
  • بلع

هناك الكثير من أوجه التشابه في ما يمكن أن يفعله هؤلاء و Webpack ، لكن الاختلاف الرئيسي هو أن تلك المعروفة باسمالعدائين المهمة، بينما وُلد webpack كمجمع وحدة.

إنها أداة أكثر تركيزًا: يمكنك تحديد نقطة دخول إلى تطبيقك (يمكن أن يكون ملف HTML به علامات نصية) وتحلل حزمة الويب الملفات والحزم كل ما تحتاجه لتشغيل التطبيق في ملف إخراج JavaScript واحد (أو في أكثر الملفات إذا كنت تستخدم تقسيم التعليمات البرمجية).

تثبيت حزمة الويب

يمكن تثبيت Webpack عالميًا أو محليًا لكل مشروع.

التثبيت العالمي

إليك كيفية تثبيته عالميًا باستخدامغزل:

yarn global add webpack webpack-cli

with npm:

npm i -g webpack webpack-cli

once this is done, you should be able to run

webpack-cli

Running webpack-cli

Local install

Webpack can be installed locally as well. It’s the recommended setup, because webpack can be updated per-project, and you have less resistance to using the latest features just for a small project rather than updating all the projects you have that use webpack.

With Yarn:

yarn add webpack webpack-cli -D

with npm:

npm i webpack webpack-cli --save-dev

Once this is done, add this to your package.json file:

{
  //...
  "scripts": {
    "build": "webpack"
  }
}

once this is done, you can run webpack by typing

yarn build

in the project root.

Webpack configuration

By default, webpack (starting from version 4) does not require any config if you respect these conventions:

  • the entry point of your app is ./src/index.js
  • the output is put in ./dist/main.js.
  • Webpack works in production mode

You can customize every little bit of webpack of course, when you need. The webpack configuration is stored in the webpack.config.js file, in the project root folder.

The entry point

By default the entry point is ./src/index.js This simple example uses the ./index.js file as a starting point:

module.exports = {
  /*...*/
  entry: './index.js'
  /*...*/
}

The output

By default the output is generated in ./dist/main.js. This example puts the output bundle into app.js:

module.exports = {
  /*...*/
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'app.js'
  }
  /*...*/
}

Loaders

Using webpack allows you to use import or require statements in your JavaScript code to not just include other JavaScript, but any kind of file, for example CSS.

Webpack aims to handle all our dependencies, not just JavaScript, and loaders are one way to do that.

For example, in your code you can use:

import 'style.css'

by using this loader configuration:

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

The regular expression targets any CSS file.

A loader can have options:

module.exports = {
  /*...*/
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: 'css-loader',
            options: {
              modules: true
            }
          }
        ]
      }
    ]
  }
  /*...*/
}

You can require multiple loaders for each rule:

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

In this example, css-loader interprets the import 'style.css' directive in the CSS. style-loader is then responsible for injecting that CSS in the DOM, using a <style> tag.

The order matters, and it’s reversed (the last is executed first).

What kind of loaders are there? Many! You can find the full list here.

A commonly used loader is Babel, which is used to transpile modern JavaScript to ES5 code:

module.exports = {
  /*...*/
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env']
          }
        }
      }
    ]
  }
  /*...*/
}

This example makes Babel preprocess all our React/JSX files:

module.exports = {
  /*...*/
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: 'babel-loader'
      }
    ]
  },
  resolve: {
    extensions: [
      '.js',
      '.jsx'
    ]
  }
  /*...*/
}

See the babel-loader options here.

Plugins

Plugins are like loaders, but on steroids. They can do things that loaders can’t do, and they are the main building block of webpack.

Take this example:

module.exports = {
  /*...*/
  plugins: [
    new HTMLWebpackPlugin()
  ]
  /*...*/
}

The HTMLWebpackPlugin plugin has the job of automatically creating an HTML file, adding the output JS bundle path, so the JavaScript is ready to be served.

There are lots of plugins available.

One useful plugin, CleanWebpackPlugin, can be used to clear the dist/ folder before creating any output, so you don’t leave files around when you change the name of the output file:

module.exports = {
  /*...*/
  plugins: [
    new CleanWebpackPlugin(['dist']),
  ]
  /*...*/
}

The webpack mode

This mode (introduced in webpack 4) sets the environment on which webpack works. It can be set to development or production (defaults to production, so you only set it when moving to development)

module.exports = {
  entry: './index.js',
  mode: 'development',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'app.js'
  }
}

Development mode:

  • builds very fast
  • is less optimized than production
  • does not remove comments
  • provides more detailed error messages and suggestions
  • provides a better debugging experience

Production mode is slower to build, since it needs to generate a more optimized bundle. The resulting JavaScript file is smaller in size, as it removes many things that are not needed in production.

I made a sample app that just prints a console.log statement.

Here’s the production bundle:

Production bundle

Here’s the development bundle:

Development bundle

Running webpack

Webpack can be run from the command line manually if installed globally, but generally you write a script inside the package.json file, which is then run using npm or yarn.

For example this package.json scripts definition we used before:

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

allows us to run webpack by running

npm run build

or

yarn run build

or

yarn build

Watching changes

Webpack can automatically rebuild the bundle when a change in your app happens, and keep listening for the next change.

Just add this script:

"scripts": {
  "watch": "webpack --watch"
}

and run

npm run watch

or

yarn run watch

or

yarn watch

One nice feature of the watch mode is that the bundle is only changed if the build has no errors. If there are errors, watch will keep listening for changes, and try to rebuild the bundle, but the current, working bundle is not affected by those problematic builds.

Handling images

Webpack allows us to use images in a very convenient way, using the file-loader loader.

This simple configuration:

module.exports = {
  /*...*/
  module: {
    rules: [
      {
        test: /\.(png|svg|jpg|gif)$/,
        use: [
          'file-loader'
        ]
      }
    ]
  }
  /*...*/
}

Allows you to import images in your JavaScript:

import Icon from './icon.png'

const img = new Image() img.src = Icon element.appendChild(img)

(img is an HTMLImageElement. Check the Image docs)

file-loader can handle other asset types as well, like fonts, CSV files, xml, and more.

Another nice tool to work with images is the url-loader loader.

This example loads any PNG file smaller than 8KB as a data URL.

module.exports = {
  /*...*/
  module: {
    rules: [
      {
        test: /\.png$/,
        use: [
          {
            loader: 'url-loader',
            options: {
              limit: 8192
            }
          }
        ]
      }
    ]
  }
  /*...*/
}

Process your SASS code and transform it to CSS

Using sass-loader, css-loader and style-loader:

module.exports = {
  /*...*/
  module: {
    rules: [
      {
        test: /\.scss$/,
        use: [
          'style-loader',
          'css-loader',
          'sass-loader'
        ]
      }
    ]
  }
  /*...*/
}

Generate Source Maps

Since webpack bundles the code, Source Maps are mandatory to get a reference to the original file that raised an error, for example.

You tell webpack to generate source maps using the devtool property of the configuration:

module.exports = {
  /*...*/
  devtool: 'inline-source-map',
  /*...*/
}

devtool has many possible values, the most used probably are:

  • none: adds no source maps
  • source-map: ideal for production, provides a separate source map that can be minimized, and adds a reference into the bundle, so development tools know that the source map is available. Of course you should configure the server to avoid shipping this, and just use it for debugging purposes
  • inline-source-map: ideal for development, inlines the source map as a Data URL

More devtools tutorials: