Lawrence  Lesch

Lawrence Lesch

1649351100

Babel-loader: Babel Loader for Webpack

This README is for babel-loader v8 + Babel v7 Check the 7.x branch for docs with Babel v6Babel logo

Babel Loader

This package allows transpiling JavaScript files using Babel and webpack.

Note: Issues with the output should be reported on the Babel Issues tracker.

Install

webpack 4.x | babel-loader 8.x | babel 7.x

npm install -D babel-loader @babel/core @babel/preset-env webpack

Usage

webpack documentation: Loaders

Within your webpack configuration object, you'll need to add the babel-loader to the list of modules, like so:

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

Options

See the babel options.

You can pass options to the loader by using the options property:

module: {
  rules: [
    {
      test: /\.m?js$/,
      exclude: /(node_modules|bower_components)/,
      use: {
        loader: 'babel-loader',
        options: {
          presets: ['@babel/preset-env'],
          plugins: ['@babel/plugin-proposal-object-rest-spread']
        }
      }
    }
  ]
}

This loader also supports the following loader-specific option:

cacheDirectory: Default false. When set, the given directory will be used to cache the results of the loader. Future webpack builds will attempt to read from the cache to avoid needing to run the potentially expensive Babel recompilation process on each run. If the value is set to true in options ({cacheDirectory: true}), the loader will use the default cache directory in node_modules/.cache/babel-loader or fallback to the default OS temporary file directory if no node_modules folder could be found in any root directory.

cacheIdentifier: Default is a string composed by the @babel/core's version, the babel-loader's version, the contents of .babelrc file if it exists, and the value of the environment variable BABEL_ENV with a fallback to the NODE_ENV environment variable. This can be set to a custom value to force cache busting if the identifier changes.

cacheCompression: Default true. When set, each Babel transform output will be compressed with Gzip. If you want to opt-out of cache compression, set it to false -- your project may benefit from this if it transpiles thousands of files.

customize: Default null. The path of a module that exports a custom callback like the one that you'd pass to .custom(). Since you already have to make a new file to use this, it is recommended that you instead use .custom to create a wrapper loader. Only use this if you must continue using babel-loader directly, but still want to customize.

Troubleshooting

babel-loader is slow!

Make sure you are transforming as few files as possible. Because you are probably matching /\.m?js$/, you might be transforming the node_modules folder or other unwanted source.

To exclude node_modules, see the exclude option in the loaders config as documented above.

You can also speed up babel-loader by as much as 2x by using the cacheDirectory option. This will cache transformations to the filesystem.

Babel is injecting helpers into each file and bloating my code!

Babel uses very small helpers for common functions such as _extend. By default, this will be added to every file that requires it.

You can instead require the Babel runtime as a separate module to avoid the duplication.

The following configuration disables automatic per-file runtime injection in Babel, requiring @babel/plugin-transform-runtime instead and making all helper references use it.

See the docs for more information.

NOTE: You must run npm install -D @babel/plugin-transform-runtime to include this in your project and @babel/runtime itself as a dependency with npm install @babel/runtime.

rules: [
  // the 'transform-runtime' plugin tells Babel to
  // require the runtime instead of inlining it.
  {
    test: /\.m?js$/,
    exclude: /(node_modules|bower_components)/,
    use: {
      loader: 'babel-loader',
      options: {
        presets: ['@babel/preset-env'],
        plugins: ['@babel/plugin-transform-runtime']
      }
    }
  }
]

NOTE: transform-runtime & custom polyfills (e.g. Promise library)

Since @babel/plugin-transform-runtime includes a polyfill that includes a custom regenerator-runtime and core-js, the following usual shimming method using webpack.ProvidePlugin will not work:

// ...
        new webpack.ProvidePlugin({
            'Promise': 'bluebird'
        }),
// ...

The following approach will not work either:

require('@babel/runtime/core-js/promise').default = require('bluebird');

var promise = new Promise;

which outputs to (using runtime):

'use strict';

var _Promise = require('@babel/runtime/core-js/promise')['default'];

require('@babel/runtime/core-js/promise')['default'] = require('bluebird');

var promise = new _Promise();

The previous Promise library is referenced and used before it is overridden.

One approach is to have a "bootstrap" step in your application that would first override the default globals before your application:

// bootstrap.js

require('@babel/runtime/core-js/promise').default = require('bluebird');

// ...

require('./app');

The Node.js API for babel has been moved to babel-core.

If you receive this message, it means that you have the npm package babel installed and are using the short notation of the loader in the webpack config (which is not valid anymore as of webpack 2.x):

  {
    test: /\.m?js$/,
    loader: 'babel',
  }

webpack then tries to load the babel package instead of the babel-loader.

To fix this, you should uninstall the npm package babel, as it is deprecated in Babel v6. (Instead, install @babel/cli or @babel/core.) In the case one of your dependencies is installing babel and you cannot uninstall it yourself, use the complete name of the loader in the webpack config:

  {
    test: /\.m?js$/,
    loader: 'babel-loader',
  }

Exclude libraries that should not be transpiled

core-js and webpack/buildin will cause errors if they are transpiled by Babel.

You will need to exclude them form babel-loader.

{
  "loader": "babel-loader",
  "options": {
    "exclude": [
      // \\ for Windows, \/ for Mac OS and Linux
      /node_modules[\\\/]core-js/,
      /node_modules[\\\/]webpack[\\\/]buildin/,
    ],
    "presets": [
      "@babel/preset-env"
    ]
  }
}

Customize config based on webpack target

Webpack supports bundling multiple targets. For cases where you may want different Babel configurations for each target (like web and node), this loader provides a target property via Babel's caller API.

For example, to change the environment targets passed to @babel/preset-env based on the webpack target:

// babel.config.js

module.exports = api => {
  return {
    plugins: [
      "@babel/plugin-proposal-nullish-coalescing-operator",
      "@babel/plugin-proposal-optional-chaining"
    ],
    presets: [
      [
        "@babel/preset-env",
        {
          useBuiltIns: "entry",
          // caller.target will be the same as the target option from webpack
          targets: api.caller(caller => caller && caller.target === "node")
            ? { node: "current" }
            : { chrome: "58", ie: "11" }
        }
      ]
    ]
  }
}

Customized Loader

babel-loader exposes a loader-builder utility that allows users to add custom handling of Babel's configuration for each file that it processes.

.custom accepts a callback that will be called with the loader's instance of babel so that tooling can ensure that it using exactly the same @babel/core instance as the loader itself.

In cases where you want to customize without actually having a file to call .custom, you may also pass the customize option with a string pointing at a file that exports your custom callback function.

Example

// Export from "./my-custom-loader.js" or whatever you want.
module.exports = require("babel-loader").custom(babel => {
  function myPlugin() {
    return {
      visitor: {},
    };
  }

  return {
    // Passed the loader options.
    customOptions({ opt1, opt2, ...loader }) {
      return {
        // Pull out any custom options that the loader might have.
        custom: { opt1, opt2 },

        // Pass the options back with the two custom options removed.
        loader,
      };
    },

    // Passed Babel's 'PartialConfig' object.
    config(cfg) {
      if (cfg.hasFilesystemConfig()) {
        // Use the normal config
        return cfg.options;
      }

      return {
        ...cfg.options,
        plugins: [
          ...(cfg.options.plugins || []),

          // Include a custom plugin in the options.
          myPlugin,
        ],
      };
    },

    result(result) {
      return {
        ...result,
        code: result.code + "\n// Generated by some custom loader",
      };
    },
  };
});
// And in your Webpack config
module.exports = {
  // ..
  module: {
    rules: [{
      // ...
      loader: path.join(__dirname, 'my-custom-loader.js'),
      // ...
    }]
  }
};

customOptions(options: Object): { custom: Object, loader: Object }

Given the loader's options, split custom options out of babel-loader's options.

config(cfg: PartialConfig): Object

Given Babel's PartialConfig object, return the options object that should be passed to babel.transform.

result(result: Result): Result

Given Babel's result object, allow loaders to make additional tweaks to it.

Author: Babel
Source Code: https://github.com/babel/babel-loader 
License: MIT License

#es6 #javascript #babel #webpack 

What is GEEK

Buddha Community

Babel-loader: Babel Loader for Webpack
Lawrence  Lesch

Lawrence Lesch

1649351100

Babel-loader: Babel Loader for Webpack

This README is for babel-loader v8 + Babel v7 Check the 7.x branch for docs with Babel v6Babel logo

Babel Loader

This package allows transpiling JavaScript files using Babel and webpack.

Note: Issues with the output should be reported on the Babel Issues tracker.

Install

webpack 4.x | babel-loader 8.x | babel 7.x

npm install -D babel-loader @babel/core @babel/preset-env webpack

Usage

webpack documentation: Loaders

Within your webpack configuration object, you'll need to add the babel-loader to the list of modules, like so:

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

Options

See the babel options.

You can pass options to the loader by using the options property:

module: {
  rules: [
    {
      test: /\.m?js$/,
      exclude: /(node_modules|bower_components)/,
      use: {
        loader: 'babel-loader',
        options: {
          presets: ['@babel/preset-env'],
          plugins: ['@babel/plugin-proposal-object-rest-spread']
        }
      }
    }
  ]
}

This loader also supports the following loader-specific option:

cacheDirectory: Default false. When set, the given directory will be used to cache the results of the loader. Future webpack builds will attempt to read from the cache to avoid needing to run the potentially expensive Babel recompilation process on each run. If the value is set to true in options ({cacheDirectory: true}), the loader will use the default cache directory in node_modules/.cache/babel-loader or fallback to the default OS temporary file directory if no node_modules folder could be found in any root directory.

cacheIdentifier: Default is a string composed by the @babel/core's version, the babel-loader's version, the contents of .babelrc file if it exists, and the value of the environment variable BABEL_ENV with a fallback to the NODE_ENV environment variable. This can be set to a custom value to force cache busting if the identifier changes.

cacheCompression: Default true. When set, each Babel transform output will be compressed with Gzip. If you want to opt-out of cache compression, set it to false -- your project may benefit from this if it transpiles thousands of files.

customize: Default null. The path of a module that exports a custom callback like the one that you'd pass to .custom(). Since you already have to make a new file to use this, it is recommended that you instead use .custom to create a wrapper loader. Only use this if you must continue using babel-loader directly, but still want to customize.

Troubleshooting

babel-loader is slow!

Make sure you are transforming as few files as possible. Because you are probably matching /\.m?js$/, you might be transforming the node_modules folder or other unwanted source.

To exclude node_modules, see the exclude option in the loaders config as documented above.

You can also speed up babel-loader by as much as 2x by using the cacheDirectory option. This will cache transformations to the filesystem.

Babel is injecting helpers into each file and bloating my code!

Babel uses very small helpers for common functions such as _extend. By default, this will be added to every file that requires it.

You can instead require the Babel runtime as a separate module to avoid the duplication.

The following configuration disables automatic per-file runtime injection in Babel, requiring @babel/plugin-transform-runtime instead and making all helper references use it.

See the docs for more information.

NOTE: You must run npm install -D @babel/plugin-transform-runtime to include this in your project and @babel/runtime itself as a dependency with npm install @babel/runtime.

rules: [
  // the 'transform-runtime' plugin tells Babel to
  // require the runtime instead of inlining it.
  {
    test: /\.m?js$/,
    exclude: /(node_modules|bower_components)/,
    use: {
      loader: 'babel-loader',
      options: {
        presets: ['@babel/preset-env'],
        plugins: ['@babel/plugin-transform-runtime']
      }
    }
  }
]

NOTE: transform-runtime & custom polyfills (e.g. Promise library)

Since @babel/plugin-transform-runtime includes a polyfill that includes a custom regenerator-runtime and core-js, the following usual shimming method using webpack.ProvidePlugin will not work:

// ...
        new webpack.ProvidePlugin({
            'Promise': 'bluebird'
        }),
// ...

The following approach will not work either:

require('@babel/runtime/core-js/promise').default = require('bluebird');

var promise = new Promise;

which outputs to (using runtime):

'use strict';

var _Promise = require('@babel/runtime/core-js/promise')['default'];

require('@babel/runtime/core-js/promise')['default'] = require('bluebird');

var promise = new _Promise();

The previous Promise library is referenced and used before it is overridden.

One approach is to have a "bootstrap" step in your application that would first override the default globals before your application:

// bootstrap.js

require('@babel/runtime/core-js/promise').default = require('bluebird');

// ...

require('./app');

The Node.js API for babel has been moved to babel-core.

If you receive this message, it means that you have the npm package babel installed and are using the short notation of the loader in the webpack config (which is not valid anymore as of webpack 2.x):

  {
    test: /\.m?js$/,
    loader: 'babel',
  }

webpack then tries to load the babel package instead of the babel-loader.

To fix this, you should uninstall the npm package babel, as it is deprecated in Babel v6. (Instead, install @babel/cli or @babel/core.) In the case one of your dependencies is installing babel and you cannot uninstall it yourself, use the complete name of the loader in the webpack config:

  {
    test: /\.m?js$/,
    loader: 'babel-loader',
  }

Exclude libraries that should not be transpiled

core-js and webpack/buildin will cause errors if they are transpiled by Babel.

You will need to exclude them form babel-loader.

{
  "loader": "babel-loader",
  "options": {
    "exclude": [
      // \\ for Windows, \/ for Mac OS and Linux
      /node_modules[\\\/]core-js/,
      /node_modules[\\\/]webpack[\\\/]buildin/,
    ],
    "presets": [
      "@babel/preset-env"
    ]
  }
}

Customize config based on webpack target

Webpack supports bundling multiple targets. For cases where you may want different Babel configurations for each target (like web and node), this loader provides a target property via Babel's caller API.

For example, to change the environment targets passed to @babel/preset-env based on the webpack target:

// babel.config.js

module.exports = api => {
  return {
    plugins: [
      "@babel/plugin-proposal-nullish-coalescing-operator",
      "@babel/plugin-proposal-optional-chaining"
    ],
    presets: [
      [
        "@babel/preset-env",
        {
          useBuiltIns: "entry",
          // caller.target will be the same as the target option from webpack
          targets: api.caller(caller => caller && caller.target === "node")
            ? { node: "current" }
            : { chrome: "58", ie: "11" }
        }
      ]
    ]
  }
}

Customized Loader

babel-loader exposes a loader-builder utility that allows users to add custom handling of Babel's configuration for each file that it processes.

.custom accepts a callback that will be called with the loader's instance of babel so that tooling can ensure that it using exactly the same @babel/core instance as the loader itself.

In cases where you want to customize without actually having a file to call .custom, you may also pass the customize option with a string pointing at a file that exports your custom callback function.

Example

// Export from "./my-custom-loader.js" or whatever you want.
module.exports = require("babel-loader").custom(babel => {
  function myPlugin() {
    return {
      visitor: {},
    };
  }

  return {
    // Passed the loader options.
    customOptions({ opt1, opt2, ...loader }) {
      return {
        // Pull out any custom options that the loader might have.
        custom: { opt1, opt2 },

        // Pass the options back with the two custom options removed.
        loader,
      };
    },

    // Passed Babel's 'PartialConfig' object.
    config(cfg) {
      if (cfg.hasFilesystemConfig()) {
        // Use the normal config
        return cfg.options;
      }

      return {
        ...cfg.options,
        plugins: [
          ...(cfg.options.plugins || []),

          // Include a custom plugin in the options.
          myPlugin,
        ],
      };
    },

    result(result) {
      return {
        ...result,
        code: result.code + "\n// Generated by some custom loader",
      };
    },
  };
});
// And in your Webpack config
module.exports = {
  // ..
  module: {
    rules: [{
      // ...
      loader: path.join(__dirname, 'my-custom-loader.js'),
      // ...
    }]
  }
};

customOptions(options: Object): { custom: Object, loader: Object }

Given the loader's options, split custom options out of babel-loader's options.

config(cfg: PartialConfig): Object

Given Babel's PartialConfig object, return the options object that should be passed to babel.transform.

result(result: Result): Result

Given Babel's result object, allow loaders to make additional tweaks to it.

Author: Babel
Source Code: https://github.com/babel/babel-loader 
License: MIT License

#es6 #javascript #babel #webpack 

Dexter  Goodwin

Dexter Goodwin

1650394920

Webpack: A Bundler for Javascript and Friends

webpack

Webpack is a module bundler. Its 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.

Install

Install with npm:

npm install --save-dev webpack

Install with yarn:

yarn add webpack --dev

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 ES Modules, 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. TypeScript to JavaScript, Handlebars strings to compiled functions, images to Base64, etc.
  • Highly modular plugin system to do whatever else your application requires.

Get Started

Check out webpack's quick Get Started guide and the other guides.

Browser Compatibility

Webpack supports all browsers that are ES5-compliant (IE8 and below are not supported). Webpack also needs Promise for import() and require.ensure(). If you want to support older browsers, you will need to load a polyfill before using these expressions.

Concepts

Plugins

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

NameStatusInstall SizeDescription
[mini-css-extract-plugin][mini-css]![mini-css-npm]![mini-css-size]Extracts CSS into separate files. It creates a CSS file per JS file which contains CSS.
[compression-webpack-plugin][compression]![compression-npm]![compression-size]Prepares compressed versions of assets to serve them with Content-Encoding
[html-webpack-plugin][html-plugin]![html-plugin-npm]![html-plugin-size]Simplifies creation of HTML files (index.html) to serve your bundles

Loaders

Webpack enables the 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.

Files

NameStatusInstall SizeDescription
[val-loader][val]![val-npm]![val-size]Executes code as module and considers exports as JS code

JSON

NameStatusInstall SizeDescription
![cson-npm]![cson-size]Loads and transpiles a CSON file

Transpiling

NameStatusInstall SizeDescription
![babel-npm]![babel-size]Loads ES2015+ code and transpiles to ES5 using Babel
![type-npm]![type-size]Loads TypeScript like JavaScript
![coffee-npm]![coffee-size]Loads CoffeeScript like JavaScript

Templating

NameStatusInstall SizeDescription
![html-npm]![html-size]Exports HTML as string, requires references to static resources
![pug-npm]![pug-size]Loads Pug templates and returns a function
![md-npm]![md-size]Compiles Markdown to HTML
![posthtml-npm]![posthtml-size]Loads and transforms a HTML file using PostHTML
![hbs-npm]![hbs-size]Compiles Handlebars to HTML

Styling

NameStatusInstall SizeDescription
<style>![style-npm]![style-size]Add exports of a module as style to DOM
![css-npm]![css-size]Loads CSS file with resolved imports and returns CSS code
![less-npm]![less-size]Loads and compiles a LESS file
![sass-npm]![sass-size]Loads and compiles a Sass/SCSS file
![stylus-npm]![stylus-size]Loads and compiles a Stylus file
![postcss-npm]![postcss-size]Loads and transforms a CSS/SSS file using PostCSS

Frameworks

NameStatusInstall SizeDescription
![vue-npm]![vue-size]Loads and compiles Vue Components
![polymer-npm]![polymer-size]Process HTML & CSS with preprocessor of choice and require() Web Components like first-class modules
![angular-npm]![angular-size]Loads and compiles Angular 2 Components
![riot-npm]![riot-size]Riot official webpack loader

Performance

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

Module Formats

Webpack supports ES2015+, CommonJS and AMD modules out of the box. 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.

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 make your code chunks cache friendly by using hashes.

Contributing

We want contributing to webpack to be fun, enjoyable, and educational for anyone, and everyone. We have a vibrant ecosystem that spans beyond this single repo. We welcome you to check out any of the repositories in our organization or webpack-contrib organization which houses all of our loaders and plugins.

Contributions go far beyond pull requests and commits. Although we love giving you the opportunity to put your stamp on webpack, we also are thrilled to receive a variety of other contributions including:

  • Documentation updates, enhancements, designs, or bugfixes
  • Spelling or grammar fixes
  • README.md corrections or redesigns
  • Adding unit, or functional tests
  • Triaging GitHub issues -- especially determining whether an issue still persists or is reproducible.
  • Searching #webpack on twitter and helping someone else who needs help
  • Teaching others how to contribute to one of the many webpack's repos!
  • Blogging, speaking about, or creating tutorials about one of webpack's many features.
  • Helping others in our webpack gitter channel.

To get started have a look at our documentation on contributing.

If you are worried or don't know where to start, you can always reach out to Sean Larkin (@TheLarkInn) on Twitter or simply submit an issue and a maintainer can help give you guidance!

We have also started a series on our Medium Publication called The Contributor's Guide to webpack. We welcome you to read it and post any questions or responses if you still need help.

Looking to speak about webpack? We'd love to review your talk abstract/CFP! You can email it to webpack [at] opencollective [dot] com and we can give pointers or tips!!!

Creating your own plugins and loaders

If you create a loader or plugin, we would <3 for you to open source it, and put it on npm. We follow the x-loader, x-webpack-plugin naming convention.

Support

We consider webpack to be a low-level tool used not only individually but also layered beneath other awesome tools. Because of its flexibility, webpack isn't always the easiest entry-level solution, however we do believe it is the most powerful. That said, we're always looking for ways to improve and simplify the tool without compromising functionality. If you have any ideas on ways to accomplish this, we're all ears!

If you're just getting started, take a look at our new docs and concepts page. This has a high level overview that is great for beginners!!

Looking for webpack 1 docs? Please check out the old wiki, but note that this deprecated version is no longer supported.

If you want to discuss something or just need help, here is our Gitter room where there are always individuals looking to help out!

If you are still having difficulty, we would love for you to post a question to StackOverflow with the webpack tag. It is much easier to answer questions that include your webpack.config.js and relevant files! So if you can provide them, we'd be extremely grateful (and more likely to help you find the answer!)

If you are twitter savvy you can tweet #webpack with your question and someone should be able to reach out and help also.

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

Sponsoring

Most of the core team members, webpack contributors and contributors in the ecosystem do this open source work in their free time. If you use webpack for a serious task, and you'd like us 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.

This is how we use the donations:

  • Allow the core team to work on webpack
  • Thank contributors if they invested a large amount of time in contributing
  • Support projects in the ecosystem that are of great value for users
  • Support projects that are voted most (work in progress)
  • Infrastructure cost
  • Fees for money handling

Author: Webpack
Source Code: https://github.com/webpack/webpack 
License: MIT License

#webpack #javascript 

Lawrence  Lesch

Lawrence Lesch

1642275180

Webpack: Packs Commonjs/AMD Modules for The Browser

webpack

Webpack is a module bundler. Its 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.

Table of Contents

  1. Install
  2. Introduction
  3. Concepts
  4. Contributing
  5. Support
  6. Core Team
  7. Sponsoring
  8. Premium Partners
  9. Other Backers and Sponsors
  10. Gold Sponsors
  11. Silver Sponsors
  12. Bronze Sponsors
  13. Backers
  14. Special Thanks

Install

Install with npm:

npm install --save-dev webpack

Install with yarn:

yarn add webpack --dev

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 ES Modules, 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. TypeScript to JavaScript, Handlebars strings to compiled functions, images to Base64, etc.
  • Highly modular plugin system to do whatever else your application requires.

Get Started

Check out webpack's quick Get Started guide and the other guides.

Browser Compatibility

Webpack supports all browsers that are ES5-compliant (IE8 and below are not supported). Webpack also needs Promise for import() and require.ensure(). If you want to support older browsers, you will need to load a polyfill before using these expressions.

Concepts

Plugins

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

NameStatusInstall SizeDescription
mini-css-extract-pluginmini-css-npmmini-css-sizeExtracts CSS into separate files. It creates a CSS file per JS file which contains CSS.
compression-webpack-plugincompression-npmcompression-sizePrepares compressed versions of assets to serve them with Content-Encoding
html-webpack-pluginhtml-plugin-npmhtml-plugin-sizeSimplifies creation of HTML files (index.html) to serve your bundles

Loaders

Webpack enables the 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.

Files

NameStatusInstall SizeDescription
val-loaderval-npmval-sizeExecutes code as module and considers exports as JS code

JSON

NameStatusInstall SizeDescription
cson-npmcson-sizeLoads and transpiles a CSON file

Transpiling

NameStatusInstall SizeDescription
babel-npmbabel-sizeLoads ES2015+ code and transpiles to ES5 using Babel
type-npmtype-sizeLoads TypeScript like JavaScript
coffee-npmcoffee-sizeLoads CoffeeScript like JavaScript

Templating

NameStatusInstall SizeDescription
html-npmhtml-sizeExports HTML as string, requires references to static resources
pug-npmpug-sizeLoads Pug templates and returns a function
md-npmmd-sizeCompiles Markdown to HTML
posthtml-npmposthtml-sizeLoads and transforms a HTML file using PostHTML
hbs-npmhbs-sizeCompiles Handlebars to HTML

Styling

NameStatusInstall SizeDescription
<style>style-npmstyle-sizeAdd exports of a module as style to DOM
css-npmcss-sizeLoads CSS file with resolved imports and returns CSS code
less-npmless-sizeLoads and compiles a LESS file
sass-npmsass-sizeLoads and compiles a Sass/SCSS file
stylus-npmstylus-sizeLoads and compiles a Stylus file
postcss-npmpostcss-sizeLoads and transforms a CSS/SSS file using PostCSS

Frameworks

NameStatusInstall SizeDescription
vue-npmvue-sizeLoads and compiles Vue Components
polymer-npmpolymer-sizeProcess HTML & CSS with preprocessor of choice and require() Web Components like first-class modules
angular-npmangular-sizeLoads and compiles Angular 2 Components
riot-npmriot-sizeRiot official webpack loader

Performance

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

Module Formats

Webpack supports ES2015+, CommonJS and AMD modules out of the box. 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.

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 make your code chunks cache friendly by using hashes.

Contributing

We want contributing to webpack to be fun, enjoyable, and educational for anyone, and everyone. We have a vibrant ecosystem that spans beyond this single repo. We welcome you to check out any of the repositories in our organization or webpack-contrib organization which houses all of our loaders and plugins.

Contributions go far beyond pull requests and commits. Although we love giving you the opportunity to put your stamp on webpack, we also are thrilled to receive a variety of other contributions including:

  • Documentation updates, enhancements, designs, or bugfixes
  • Spelling or grammar fixes
  • README.md corrections or redesigns
  • Adding unit, or functional tests
  • Triaging GitHub issues -- especially determining whether an issue still persists or is reproducible.
  • Searching #webpack on twitter and helping someone else who needs help
  • Teaching others how to contribute to one of the many webpack's repos!
  • Blogging, speaking about, or creating tutorials about one of webpack's many features.
  • Helping others in our webpack gitter channel.

To get started have a look at our documentation on contributing.

If you are worried or don't know where to start, you can always reach out to Sean Larkin (@TheLarkInn) on Twitter or simply submit an issue and a maintainer can help give you guidance!

We have also started a series on our Medium Publication called The Contributor's Guide to webpack. We welcome you to read it and post any questions or responses if you still need help.

Looking to speak about webpack? We'd love to review your talk abstract/CFP! You can email it to webpack [at] opencollective [dot] com and we can give pointers or tips!!!

Creating your own plugins and loaders

If you create a loader or plugin, we would <3 for you to open source it, and put it on npm. We follow the x-loader, x-webpack-plugin naming convention.

Support

We consider webpack to be a low-level tool used not only individually but also layered beneath other awesome tools. Because of its flexibility, webpack isn't always the easiest entry-level solution, however we do believe it is the most powerful. That said, we're always looking for ways to improve and simplify the tool without compromising functionality. If you have any ideas on ways to accomplish this, we're all ears!

If you're just getting started, take a look at our new docs and concepts page. This has a high level overview that is great for beginners!!

Looking for webpack 1 docs? Please check out the old wiki, but note that this deprecated version is no longer supported.

If you want to discuss something or just need help, here is our Gitter room where there are always individuals looking to help out!

If you are still having difficulty, we would love for you to post a question to StackOverflow with the webpack tag. It is much easier to answer questions that include your webpack.config.js and relevant files! So if you can provide them, we'd be extremely grateful (and more likely to help you find the answer!)

If you are twitter savvy you can tweet #webpack with your question and someone should be able to reach out and help also.

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

Author: Webpack
Source Code: https://github.com/webpack/webpack 
License: MIT License

#webpack #javascript 

Lawrence  Lesch

Lawrence Lesch

1672720021

TS-loader: TypeScript Loader for Webpack

TypeScript loader for webpack

ts-loader

This is the TypeScript loader for webpack.

Getting Started

Installation

yarn add ts-loader --dev

or

npm install ts-loader --save-dev

You will also need to install TypeScript if you have not already.

yarn add typescript --dev

or

npm install typescript --save-dev

Running

Use webpack like normal, including webpack --watch and webpack-dev-server, or through another build system using the Node.js API.

Examples

We have a number of example setups to accommodate different workflows. Our examples can be found here.

We probably have more examples than we need. That said, here's a good way to get started:

  • I want the simplest setup going. Use "vanilla" ts-loader
  • I want the fastest compilation that's available. Use fork-ts-checker-webpack-plugin. It performs type checking in a separate process with ts-loader just handling transpilation.

Faster Builds

As your project becomes bigger, compilation time increases linearly. It's because typescript's semantic checker has to inspect all files on every rebuild. The simple solution is to disable it by using the transpileOnly: true option, but doing so leaves you without type checking and will not output declaration files.

You probably don't want to give up type checking; that's rather the point of TypeScript. So what you can do is use the fork-ts-checker-webpack-plugin. It runs the type checker on a separate process, so your build remains fast thanks to transpileOnly: true but you still have the type checking.

If you'd like to see a simple setup take a look at our example.

Yarn Plug’n’Play

ts-loader supports Yarn Plug’n’Play. The recommended way to integrate is using the pnp-webpack-plugin.

Babel

ts-loader works very well in combination with babel and babel-loader. There is an example of this in the official TypeScript Samples.

Compatibility

  • TypeScript: 3.6.3+
  • webpack: 5.x+ (please use ts-loader 8.x if you need webpack 4 support)
  • node: 12.x+

A full test suite runs each night (and on each pull request). It runs both on Linux and Windows, testing ts-loader against major releases of TypeScript. The test suite also runs against TypeScript@next (because we want to use it as much as you do).

If you become aware of issues not caught by the test suite then please let us know. Better yet, write a test and submit it in a PR!

Configuration

Create or update webpack.config.js like so:

module.exports = {
  mode: "development",
  devtool: "inline-source-map",
  entry: "./app.ts",
  output: {
    filename: "bundle.js"
  },
  resolve: {
    // Add `.ts` and `.tsx` as a resolvable extension.
    extensions: [".ts", ".tsx", ".js"],
    // Add support for TypeScripts fully qualified ESM imports.
    extensionAlias: {
     ".js": [".js", ".ts"],
     ".cjs": [".cjs", ".cts"],
     ".mjs": [".mjs", ".mts"]
    }
  },
  module: {
    rules: [
      // all files with a `.ts`, `.cts`, `.mts` or `.tsx` extension will be handled by `ts-loader`
      { test: /\.([cm]?ts|tsx)$/, loader: "ts-loader" }
    ]
  }
};

Add a tsconfig.json file. (The one below is super simple; but you can tweak this to your hearts desire)

{
  "compilerOptions": {
    "sourceMap": true
  }
}

The tsconfig.json file controls TypeScript-related options so that your IDE, the tsc command, and this loader all share the same options.

devtool / sourcemaps

If you want to be able to debug your original source then you can thanks to the magic of sourcemaps. There are 2 steps to getting this set up with ts-loader and webpack.

First, for ts-loader to produce sourcemaps, you will need to set the tsconfig.json option as "sourceMap": true.

Second, you need to set the devtool option in your webpack.config.js to support the type of sourcemaps you want. To make your choice have a read of the devtool webpack docs. You may be somewhat daunted by the choice available. You may also want to vary the sourcemap strategy depending on your build environment. Here are some example strategies for different environments:

  • devtool: 'inline-source-map' - Solid sourcemap support; the best "all-rounder". Works well with karma-webpack (not all strategies do)
  • devtool: 'eval-cheap-module-source-map' - Best support for sourcemaps whilst debugging.
  • devtool: 'source-map' - Approach that plays well with UglifyJsPlugin; typically you might use this in Production

Code Splitting and Loading Other Resources

Loading css and other resources is possible but you will need to make sure that you have defined the require function in a declaration file.

declare var require: {
  <T>(path: string): T;
  (paths: string[], callback: (...modules: any[]) => void): void;
  ensure: (
    paths: string[],
    callback: (require: <T>(path: string) => T) => void
  ) => void;
};

Then you can simply require assets or chunks per the webpack documentation.

require("!style!css!./style.css");

The same basic process is required for code splitting. In this case, you import modules you need but you don't directly use them. Instead you require them at split points. See this example and this example for more details.

TypeScript 2.4 provides support for ECMAScript's new import() calls. These calls import a module and return a promise to that module. This is also supported in webpack - details on usage can be found here. Happy code splitting!

Declaration Files (.d.ts)

To output declaration files (.d.ts), you can set "declaration": true in your tsconfig and set "transpileOnly" to false.

If you use ts-loader with "transpileOnly": true along with fork-ts-checker-webpack-plugin, you will need to configure fork-ts-checker-webpack-plugin to output definition files, you can learn more on the plugin's documentation page: https://github.com/TypeStrong/fork-ts-checker-webpack-plugin#typescript-options

To output a built .d.ts file, you can use the DeclarationBundlerPlugin in your webpack config.

Failing the build on TypeScript compilation error

The build should fail on TypeScript compilation errors as of webpack 2. If for some reason it does not, you can use the webpack-fail-plugin.

For more background have a read of this issue.

baseUrl / paths module resolution

If you want to resolve modules according to baseUrl and paths in your tsconfig.json then you can use the tsconfig-paths-webpack-plugin package. For details about this functionality, see the module resolution documentation.

This feature requires webpack 2.1+ and TypeScript 2.0+. Use the config below or check the package for more information on usage.

const TsconfigPathsPlugin = require('tsconfig-paths-webpack-plugin');

module.exports = {
  ...
  resolve: {
    plugins: [new TsconfigPathsPlugin({ configFile: "./path/to/tsconfig.json" })]
  }
  ...
}

Options

There are two types of options: TypeScript options (aka "compiler options") and loader options. TypeScript options should be set using a tsconfig.json file. Loader options can be specified through the options property in the webpack configuration:

module.exports = {
  ...
  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: [
          {
            loader: 'ts-loader',
            options: {
              transpileOnly: true
            }
          }
        ]
      }
    ]
  }
}

Loader Options

transpileOnly

TypeDefault Value
booleanfalse

If you want to speed up compilation significantly you can set this flag. However, many of the benefits you get from static type checking between different dependencies in your application will be lost. transpileOnly will not speed up compilation of project references.

It's advisable to use transpileOnly alongside the fork-ts-checker-webpack-plugin to get full type checking again. To see what this looks like in practice then either take a look at our example.

Tip: When you add the fork-ts-checker-webpack-plugin to your webpack config, the transpileOnly will default to true, so you can skip that option.

If you enable this option, webpack 4 will give you "export not found" warnings any time you re-export a type:

WARNING in ./src/bar.ts
1:0-34 "export 'IFoo' was not found in './foo'
 @ ./src/bar.ts
 @ ./src/index.ts

The reason this happens is that when typescript doesn't do a full type check, it does not have enough information to determine whether an imported name is a type or not, so when the name is then exported, typescript has no choice but to emit the export. Fortunately, the extraneous export should not be harmful, so you can just suppress these warnings:

module.exports = {
  ...
  stats: {
    warningsFilter: /export .* was not found in/
  }
}

happyPackMode

TypeDefault Value
booleanfalse

If you're using HappyPack or thread-loader to parallelise your builds then you'll need to set this to true. This implicitly sets *transpileOnly* to true and WARNING! stops registering all errors to webpack.

It's advisable to use this with the fork-ts-checker-webpack-plugin to get full type checking again. IMPORTANT: If you are using fork-ts-checker-webpack-plugin alongside HappyPack or thread-loader then ensure you set the syntactic diagnostic option like so:

        new ForkTsCheckerWebpackPlugin({
          typescript: {
            diagnosticOptions: {
              semantic: true,
              syntactic: true,
            },
          },
        })

This will ensure that the plugin checks for both syntactic errors (eg const array = [{} {}];) and semantic errors (eg const x: number = '1';). By default the plugin only checks for semantic errors (as when used with ts-loader in transpileOnly mode, ts-loader will still report syntactic errors).

Also, if you are using thread-loader in watch mode, remember to set poolTimeout: Infinity so workers don't die.

resolveModuleName and resolveTypeReferenceDirective

These options should be functions which will be used to resolve the import statements and the <reference types="..."> directives instead of the default TypeScript implementation. It's not intended that these will typically be used by a user of ts-loader - they exist to facilitate functionality such as Yarn Plug’n’Play.

getCustomTransformers

Type
(program: Program, getProgram: () => Program) => { before?: TransformerFactory<SourceFile>[]; after?: TransformerFactory<SourceFile>[]; afterDeclarations?: TransformerFactory<SourceFile>[]; }

Provide custom transformers - only compatible with TypeScript 2.3+ (and 2.4 if using transpileOnly mode). For example usage take a look at typescript-plugin-styled-components or our test.

You can also pass a path string to locate a js module file which exports the function described above, this useful especially in happyPackMode. (Because forked processes cannot serialize functions see more at related issue)

logInfoToStdOut

TypeDefault Value
booleanfalse

This is important if you read from stdout or stderr and for proper error handling. The default value ensures that you can read from stdout e.g. via pipes or you use webpack -j to generate json output.

logLevel

TypeDefault Value
stringwarn

Can be info, warn or error which limits the log output to the specified log level. Beware of the fact that errors are written to stderr and everything else is written to stderr (or stdout if logInfoToStdOut is true).

silent

TypeDefault Value
booleanfalse

If true, no console.log messages will be emitted. Note that most error messages are emitted via webpack which is not affected by this flag.

ignoreDiagnostics

TypeDefault Value
number[][]

You can squelch certain TypeScript errors by specifying an array of diagnostic codes to ignore.

reportFiles

TypeDefault Value
string[][]

Only report errors on files matching these glob patterns.

  // in webpack.config.js
  {
    test: /\.ts$/,
    loader: 'ts-loader',
    options: { reportFiles: ['src/**/*.{ts,tsx}', '!src/skip.ts'] }
  }

This can be useful when certain types definitions have errors that are not fatal to your application.

compiler

TypeDefault Value
string'typescript'

Allows use of TypeScript compilers other than the official one. Should be set to the NPM name of the compiler, eg ntypescript.

configFile

TypeDefault Value
string'tsconfig.json'

Allows you to specify where to find the TypeScript configuration file.

You may provide

  • just a file name. The loader then will search for the config file of each entry point in the respective entry point's containing folder. If a config file cannot be found there, it will travel up the parent directory chain and look for the config file in those folders.
  • a relative path to the configuration file. It will be resolved relative to the respective .ts entry file.
  • an absolute path to the configuration file.

Please note, that if the configuration file is outside of your project directory, you might need to set the context option to avoid TypeScript issues (like TS18003). In this case the configFile should point to the tsconfig.json and context to the project root.

colors

TypeDefault Value
booleantrue

If false, disables built-in colors in logger messages.

errorFormatter

TypeDefault Value
(message: ErrorInfo, colors: boolean) => stringundefined

By default ts-loader formats TypeScript compiler output for an error or a warning in the style:

[tsl] ERROR in myFile.ts(3,14)
      TS4711: you did something very wrong

If that format is not to your taste you can supply your own formatter using the errorFormatter option. Below is a template for a custom error formatter. Please note that the colors parameter is an instance of chalk which you can use to color your output. (This instance will respect the colors option.)

function customErrorFormatter(error, colors) {
  const messageColor =
    error.severity === "warning" ? colors.bold.yellow : colors.bold.red;
  return (
    "Does not compute.... " +
    messageColor(Object.keys(error).map(key => `${key}: ${error[key]}`))
  );
}

If the above formatter received an error like this:

{
  "code":2307,
  "severity": "error",
  "content": "Cannot find module 'components/myComponent2'.",
  "file":"/.test/errorFormatter/app.ts",
  "line":2,
  "character":31
}

It would produce an error message that said:

Does not compute.... code: 2307,severity: error,content: Cannot find module 'components/myComponent2'.,file: /.test/errorFormatter/app.ts,line: 2,character: 31

And the bit after "Does not compute.... " would be red.

compilerOptions

TypeDefault Value
object{}

Allows overriding TypeScript options. Should be specified in the same format as you would do for the compilerOptions property in tsconfig.json.

instance

TypeDefault Value
stringTODO

Advanced option to force files to go through different instances of the TypeScript compiler. Can be used to force segregation between different parts of your code.

appendTsSuffixTo

TypeDefault Value
(RegExp | string)[][]

appendTsxSuffixTo

TypeDefault Value
(RegExp | string)[][]

A list of regular expressions to be matched against filename. If filename matches one of the regular expressions, a .ts or .tsx suffix will be appended to that filename. If you're using HappyPack or thread-loader with ts-loader, you need use the string type for the regular expressions, not RegExp object.

// change this:
{ appendTsSuffixTo: [/\.vue$/] }
// to:
{ appendTsSuffixTo: ['\\.vue$'] }

This is useful for *.vue file format for now. (Probably will benefit from the new single file format in the future.)

Example:

webpack.config.js:

module.exports = {
  entry: "./index.vue",
  output: { filename: "bundle.js" },
  resolve: {
    extensions: [".ts", ".vue"]
  },
  module: {
    rules: [
      { test: /\.vue$/, loader: "vue-loader" },
      {
        test: /\.ts$/,
        loader: "ts-loader",
        options: { appendTsSuffixTo: [/\.vue$/] }
      }
    ]
  }
};

index.vue

<template><p>hello {{msg}}</p></template>
<script lang="ts">
export default {
  data(): Object {
    return {
      msg: "world"
    };
  }
};
</script>

We can handle .tsx by quite similar way:

webpack.config.js:

module.exports = {
    entry: './index.vue',
    output: { filename: 'bundle.js' },
    resolve: {
        extensions: ['.ts', '.tsx', '.vue', '.vuex']
    },
    module: {
        rules: [
            { test: /\.vue$/, loader: 'vue-loader',
              options: {
                loaders: {
                  ts: 'ts-loader',
                  tsx: 'babel-loader!ts-loader',
                }
              }
            },
            { test: /\.ts$/, loader: 'ts-loader', options: { appendTsSuffixTo: [/TS\.vue$/] } }
            { test: /\.tsx$/, loader: 'babel-loader!ts-loader', options: { appendTsxSuffixTo: [/TSX\.vue$/] } }
        ]
    }
}

tsconfig.json (set jsx option to preserve to let babel handle jsx)

{
  "compilerOptions": {
    "jsx": "preserve"
  }
}

index.vue

<script lang="tsx">
export default {
  functional: true,
  render(h, c) {
    return (<div>Content</div>);
  }
}
</script>

Or if you want to use only tsx, just use the appendTsxSuffixTo option only:

            { test: /\.ts$/, loader: 'ts-loader' }
            { test: /\.tsx$/, loader: 'babel-loader!ts-loader', options: { appendTsxSuffixTo: [/\.vue$/] } }

onlyCompileBundledFiles

TypeDefault Value
booleanfalse

The default behavior of ts-loader is to act as a drop-in replacement for the tsc command, so it respects the include, files, and exclude options in your tsconfig.json, loading any files specified by those options. The onlyCompileBundledFiles option modifies this behavior, loading only those files that are actually bundled by webpack, as well as any .d.ts files included by the tsconfig.json settings. .d.ts files are still included because they may be needed for compilation without being explicitly imported, and therefore not picked up by webpack.

useCaseSensitiveFileNames

TypeDefault Value
booleandetermined by typescript based on platform

The default behavior of ts-loader is to act as a drop-in replacement for the tsc command, so it respects the useCaseSensitiveFileNames set internally by typescript. The useCaseSensitiveFileNames option modifies this behavior, by changing the way in which ts-loader resolves file paths to compile. Setting this to true can have some performance benefits due to simplifying the file resolution codepath.

allowTsInNodeModules

TypeDefault Value
booleanfalse

By default, ts-loader will not compile .ts files in node_modules. You should not need to recompile .ts files there, but if you really want to, use this option. Note that this option acts as a whitelist - any modules you desire to import must be included in the "files" or "include" block of your project's tsconfig.json.

See: microsoft/TypeScript#12358

  // in webpack.config.js
  {
    test: /\.ts$/,
    loader: 'ts-loader',
    options: { allowTsInNodeModules: true }
  }

And in your tsconfig.json:

  {
    "include": [
      "node_modules/whitelisted_module.ts"
    ],
    "files": [
      "node_modules/my_module/whitelisted_file.ts"
    ]
  }

context

TypeDefault Value
stringundefined

If set, will parse the TypeScript configuration file with given absolute path as base path. Per default the directory of the configuration file is used as base path. Relative paths in the configuration file are resolved with respect to the base path when parsed. Option context allows to set option configFile to a path other than the project root (e.g. a NPM package), while the base path for ts-loader can remain the project root.

Keep in mind that not having a tsconfig.json in your project root can cause different behaviour between ts-loader and tsc. When using editors like VS Code it is advised to add a tsconfig.json file to the root of the project and extend the config file referenced in option configFile. For more information please read the PR that is the base and read the PR that contributed this option.

webpack:

{
  loader: require.resolve('ts-loader'),
  options: {
    context: __dirname,
    configFile: require.resolve('ts-config-react-app')
  }
}

Extending tsconfig.json:

{ "extends": "./node_modules/ts-config-react-app/index" }

Note that changes in the extending file while not be respected by ts-loader. Its purpose is to satisfy the code editor.

experimentalFileCaching

TypeDefault Value
booleantrue

By default whenever the TypeScript compiler needs to check that a file/directory exists or resolve symlinks it makes syscalls. It does not cache the result of these operations and this may result in many syscalls with the same arguments (see comment with example). In some cases it may produce performance degradation.

This flag enables caching for some FS-functions like fileExists, realpath and directoryExists for TypeScript compiler. Note that caches are cleared between compilations.

projectReferences

TypeDefault Value
booleanfalse

ts-loader has opt-in support for project references. With this configuration option enabled, ts-loader will incrementally rebuild upstream projects the same way tsc --build does. Otherwise, source files in referenced projects will be treated as if they’re part of the root project.

In order to make use of this option your project needs to be correctly configured to build the project references and then to use them as part of the build. See the Project References Guide and the example code in the examples which can be found here.

Usage with webpack watch

Because TS will generate .js and .d.ts files, you should ignore these files, otherwise watchers may go into an infinite watch loop. For example, when using webpack, you may wish to add this to your webpack.conf.js file:

// for webpack 4
 plugins: [
   new webpack.WatchIgnorePlugin([
     /\.js$/,
     /\.d\.[cm]?ts$/
   ])
 ],

// for webpack 5
plugins: [
  new webpack.WatchIgnorePlugin({
    paths:[
      /\.js$/,
      /\.d\.[cm]ts$/
  ]})
],

It's worth noting that use of the LoaderOptionsPlugin is only supposed to be a stopgap measure. You may want to look at removing it entirely.

Hot Module replacement

We do not support HMR as we did not yet work out a reliable way how to set it up.

If you want to give webpack-dev-server HMR a try, follow the official webpack HMR guide, then tweak a few config options for ts-loader:

  1. Set transpileOnly to true (see transpileOnly for config details and recommendations above).
  2. Inside your HMR acceptance callback function, maybe re-require the module that was replaced.

Contributing

This is your TypeScript loader! We want you to help make it even better. Please feel free to contribute; see the contributor's guide to get started.

History

ts-loader was started by James Brantly, since 2016 John Reilly has been taking good care of it. If you're interested, you can read more about how that came to pass.

Download Details:

Author: TypeStrong
Source Code: https://github.com/TypeStrong/ts-loader 
License: MIT license

#typescript #webpack #loader 

Dexter  Goodwin

Dexter Goodwin

1659467280

istanbul-loader: A Code Coverage-instrumenting Webpack Loader

istanbul-loader

This is a webpack loader that uses istanbul-lib-instrument to add code coverage instrumentation to JavaScript files.

Installation

Install with

npm install @theintern/istanbul-loader --save-dev

Usage

Install the loader in a project and add an entry for it to the project's webpack.config:

module: {
    rules: [
        {
            test: /src\/.*\.ts$/,
            use: '@theintern/istanbul-loader'
        },
        ...
    ]
}

Note that the istanbul-loader should be run after transpilers such as TypeScript. This means that it should come before transpilers in a loader list, or use enforce: 'post':

rules: [
    {
        test: /src\/.(\.ts$/,
        use: [ '@theintern/istanbul-loader', 'ts-node' ]
    },
    ...
]

or

rules: [
    {
        test: /src\/.(\.ts$/,
        use: '@theintern/istanbul-loader',
        enforce: 'post'
    },
    ...
]

Configuration

The rule test should only match source files, not all .ts or .js files, so as not to instrument tests or support files.

Options can be passed using the standard webpack options property:

rules: [
    {
        test: /src\/.(\.ts$/,
        use: {
            loader: '@theintern/istanbul-loader',
            options: { config: 'tests/intern.json' }
        }
    },
    ...
]

Currently the only option used by the loader is 'config', which should point to an Intern config file. The loader will use values for coverageVariable and instrumenterOptions from the Intern config, if present.

Download Details: 

Author: Theintern
Source Code: https://github.com/theintern/istanbul-loader 
License: View license

#typescript #loader #webpack