uglifyjs-webpack-plugin

What is uglifyjs-webpack-plugin?

The uglifyjs-webpack-plugin is a plugin for Webpack that uses UglifyJS to minify JavaScript files. It helps in reducing the size of JavaScript files by removing unnecessary characters, comments, and whitespace, and by optimizing the code.

What are uglifyjs-webpack-plugin's main functionalities?

Basic Minification

This feature allows you to perform basic minification of JavaScript files using UglifyJS. The code sample demonstrates how to configure the plugin in a Webpack configuration file to minimize the output JavaScript files.

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
  optimization: {
    minimizer: [new UglifyJsPlugin()]
  }
};

Custom UglifyJS Options

This feature allows you to customize the UglifyJS options. The code sample shows how to configure the plugin to remove console statements from the output JavaScript files.

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        uglifyOptions: {
          compress: {
            drop_console: true,
          },
        },
      }),
    ],
  },
};

Source Map Support

This feature enables source map support, which helps in debugging minified code. The code sample demonstrates how to configure the plugin to generate source maps for the minified JavaScript files.

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
  devtool: 'source-map',
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        sourceMap: true,
      }),
    ],
  },
};

Other packages similar to uglifyjs-webpack-plugin

terser-webpack-plugin

The terser-webpack-plugin is a Webpack plugin that uses Terser to minify JavaScript files. Terser is a fork of UglifyJS with better support for ES6+ syntax. It is often preferred over uglifyjs-webpack-plugin for modern JavaScript projects due to its better handling of newer JavaScript features.

babel-minify-webpack-plugin

The babel-minify-webpack-plugin is a Webpack plugin that uses Babel Minify (babel-minify) to minify JavaScript files. It is designed to work seamlessly with Babel and offers a wide range of minification options. It is a good alternative to uglifyjs-webpack-plugin, especially if you are already using Babel in your project.

closure-webpack-plugin

The closure-webpack-plugin is a Webpack plugin that uses Google Closure Compiler to minify JavaScript files. It offers advanced optimizations and is capable of performing aggressive code transformations. It is suitable for large projects that require high levels of optimization and code analysis.

README

UglifyJS Webpack Plugin

This plugin uses uglify-js to minify your JavaScript.

Requirements

This module requires a minimum of Node v6.9.0 and Webpack v4.0.0.

Getting Started

To begin, you'll need to install uglifyjs-webpack-plugin:

$ npm install uglifyjs-webpack-plugin --save-dev

Then add the plugin to your webpack config. For example:

webpack.config.js

const UglifyJsPlugin = require('uglifyjs-webpack-plugin');

module.exports = {
  optimization: {
    minimizer: [new UglifyJsPlugin()],
  },
};

And run webpack via your preferred method.

Options

test

Type: String|RegExp|Array<String|RegExp> Default: /\.js(\?.*)?$/i

Test to match files against.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        test: /\.js(\?.*)?$/i,
      }),
    ],
  },
};

include

Type: String|RegExp|Array<String|RegExp> Default: undefined

Files to include.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        include: /\/includes/,
      }),
    ],
  },
};

exclude

Type: String|RegExp|Array<String|RegExp> Default: undefined

Files to exclude.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        exclude: /\/excludes/,
      }),
    ],
  },
};

chunkFilter

Type: Function<(chunk) -> boolean> Default: () => true

Allowing to filter which chunks should be uglified (by default all chunks are uglified). Return true to uglify the chunk, false otherwise.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        chunkFilter: (chunk) => {
          // Exclude uglification for the `vendor` chunk
          if (chunk.name === 'vendor') {
            return false;
          }

          return true;
        },
      }),
    ],
  },
};

cache

Type: Boolean|String Default: false

Enable file caching. Default path to cache directory: node_modules/.cache/uglifyjs-webpack-plugin.

ℹ️ If you use your own minify function please read the minify section for cache invalidation correctly.

Boolean

Enable/disable file caching.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
      }),
    ],
  },
};

String

Enable file caching and set path to cache directory.

webpack.config.js

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: 'path/to/cache',
      }),
    ],
  },
};

cacheKeys

Type: Function<(defaultCacheKeys, file) -> Object> Default: defaultCacheKeys => defaultCacheKeys

Allows you to override default cache keys.

Default cache keys:

({
  'uglify-js': require('uglify-js/package.json').version, // uglify version
  'uglifyjs-webpack-plugin': require('../package.json').version, // plugin version
  'uglifyjs-webpack-plugin-options': this.options, // plugin options
  path: compiler.outputPath ? `${compiler.outputPath}/${file}` : file, // asset path
  hash: crypto
    .createHash('md4')
    .update(input)
    .digest('hex'), // source file hash
});

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        cacheKeys: (defaultCacheKeys, file) => {
          defaultCacheKeys.myCacheKey = 'myCacheKeyValue';

          return defaultCacheKeys;
        },
      }),
    ],
  },
};

parallel

Type: Boolean|Number Default: false

Use multi-process parallel running to improve the build speed. Default number of concurrent runs: os.cpus().length - 1.

ℹ️ Parallelization can speedup your build significantly and is therefore highly recommended.

Boolean

Enable/disable multi-process parallel running.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        parallel: true,
      }),
    ],
  },
};

Number

Enable multi-process parallel running and set number of concurrent runs.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        parallel: 4,
      }),
    ],
  },
};

sourceMap

Type: Boolean Default: false

Use source maps to map error message locations to modules (this slows down the compilation). If you use your own minify function please read the minify section for handling source maps correctly.

⚠️ cheap-source-map options don't work with this plugin.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        sourceMap: true,
      }),
    ],
  },
};

minify

Type: Function Default: undefined

Allows you to override default minify function. By default plugin uses uglify-js package. Useful for using and testing unpublished versions or forks.

⚠️ Always use require inside minify function when parallel option enabled.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        minify(file, sourceMap) {
          const extractedComments = [];

          // Custom logic for extract comments

          const { error, map, code, warnings } = require('uglify-module') // Or require('./path/to/uglify-module')
            .minify(file, {
              /* Your options for minification */
            });

          return { error, map, code, warnings, extractedComments };
        },
      }),
    ],
  },
};

uglifyOptions

Type: Object Default: default

UglifyJS minify options.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        uglifyOptions: {
          warnings: false,
          parse: {},
          compress: {},
          mangle: true, // Note `mangle.properties` is `false` by default.
          output: null,
          toplevel: false,
          nameCache: null,
          ie8: false,
          keep_fnames: false,
        },
      }),
    ],
  },
};

extractComments

Type: Boolean|String|RegExp|Function<(node, comment) -> Boolean|Object> Default: false

Whether comments shall be extracted to a separate file, (see details). By default extract only comments using /^\**!|@preserve|@license|@cc_on/i regexp condition and remove remaining comments. If the original file is named foo.js, then the comments will be stored to foo.js.LICENSE. The uglifyOptions.output.comments option specifies whether the comment will be preserved, i.e. it is possible to preserve some comments (e.g. annotations) while extracting others or even preserving comments that have been extracted.

Boolean

Enable/disable extracting comments.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: true,
      }),
    ],
  },
};

String

Extract all or some (use /^\**!|@preserve|@license|@cc_on/i RegExp) comments.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: 'all',
      }),
    ],
  },
};

RegExp

All comments that match the given expression will be extracted to the separate file.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: /@extract/i,
      }),
    ],
  },
};

Function<(node, comment) -> Boolean>

All comments that match the given expression will be extracted to the separate file.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: function(astNode, comment) {
          if (/@extract/i.test(comment.value)) {
            return true;
          }

          return false;
        },
      }),
    ],
  },
};

Object

Allow to customize condition for extract comments, specify extracted file name and banner.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: {
          condition: /^\**!|@preserve|@license|@cc_on/i,
          filename(file) {
            return `${file}.LICENSE`;
          },
          banner(licenseFile) {
            return `License information can be found in ${licenseFile}`;
          },
        },
      }),
    ],
  },
};

condition

Type: Boolean|String|RegExp|Function<(node, comment) -> Boolean|Object>

Condition what comments you need extract.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: {
          condition: 'some',
          filename(file) {
            return `${file}.LICENSE`;
          },
          banner(licenseFile) {
            return `License information can be found in ${licenseFile}`;
          },
        },
      }),
    ],
  },
};

filename

Type: Regex|Function<(string) -> String> Default: ${file}.LICENSE

The file where the extracted comments will be stored. Default is to append the suffix .LICENSE to the original filename.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: {
          condition: /^\**!|@preserve|@license|@cc_on/i,
          filename: 'extracted-comments.js',
          banner(licenseFile) {
            return `License information can be found in ${licenseFile}`;
          },
        },
      }),
    ],
  },
};

banner

Type: Boolean|String|Function<(string) -> String> Default: /*! For license information please see ${commentsFile} */

The banner text that points to the extracted file and will be added on top of the original file. Can be false (no banner), a String, or a Function<(string) -> String> that will be called with the filename where extracted comments have been stored. Will be wrapped into comment.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        extractComments: {
          condition: true,
          filename(file) {
            return `${file}.LICENSE`;
          },
          banner(commentsFile) {
            return `My custom banner about license information ${commentsFile}`;
          },
        },
      }),
    ],
  },
};

warningsFilter

Type: Function<(warning, source) -> Boolean> Default: () => true

Allow to filter uglify-js warnings. Return true to keep the warning, false otherwise.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        warningsFilter: (warning, source) => {
          if (/Dropping unreachable code/i.test(warning)) {
            return true;
          }

          if (/filename\.js/i.test(source)) {
            return true;
          }

          return false;
        },
      }),
    ],
  },
};

Examples

Cache And Parallel

Enable cache and multi-process parallel running.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        cache: true,
        parallel: true,
      }),
    ],
  },
};

Preserve Comments

Extract all legal comments (i.e. /^\**!|@preserve|@license|@cc_on/i) and preserve /@license/i comments.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        uglifyOptions: {
          output: {
            comments: /@license/i,
          },
        },
        extractComments: true,
      }),
    ],
  },
};

Remove Comments

If you avoid building with comments, set uglifyOptions.output.comments to false as in this config:

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        uglifyOptions: {
          output: {
            comments: false,
          },
        },
      }),
    ],
  },
};

Custom Minify Function

Override default minify function - use terser for minification.

webpack.config.js

module.exports = {
  optimization: {
    minimizer: [
      new UglifyJsPlugin({
        // Uncomment lines below for cache invalidation correctly
        // cache: true,
        // cacheKeys(defaultCacheKeys) {
        //   delete defaultCacheKeys['uglify-js'];
        //
        //   return Object.assign(
        //     {},
        //     defaultCacheKeys,
        //     { 'uglify-js': require('uglify-js/package.json').version },
        //   );
        // },
        minify(file, sourceMap) {
          // https://github.com/mishoo/UglifyJS2#minify-options
          const uglifyJsOptions = {
            /* your `uglify-js` package options */
          };

          if (sourceMap) {
            uglifyJsOptions.sourceMap = {
              content: sourceMap,
            };
          }

          return require('terser').minify(file, uglifyJsOptions);
        },
      }),
    ],
  },
};

Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

CONTRIBUTING

License

MIT