grunt-contrib-uglify

grunt-contrib-uglify v5.2.1

Minify JavaScript files with UglifyJS

Getting Started

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install grunt-contrib-uglify --save-dev

Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:

grunt.loadNpmTasks('grunt-contrib-uglify');

Uglify task

Run this task with the grunt uglify command.

Task targets, files and options may be specified according to the grunt Configuring tasks guide.

Options

This task primarily delegates to UglifyJS, so please consider their documentation as required reading for advanced configuration.

Deprecated options from 2.x

mangle

Type: Boolean Object
Default: {}

Turn on or off mangling with default options. If an Object is specified, it is passed directly to ast.mangle_names() and ast.compute_char_frequency() (mimicking command line behavior). View all options here.

compress

Type: Boolean Object
Default: {}

Turn on or off source compression with default options. If an Object is specified, it is passed as options to UglifyJS.Compressor(). View all options here.

beautify

Type: Boolean Object
Default: false

Turns on beautification of the generated source code. View all options here

parse.expression

Type: Boolean
Default: false

Parse a single expression, rather than a program (for parsing JSON)

report

Type: string
Choices: 'min', 'gzip'
Default: 'min'

Report minification result or both minification and gzip results. This is useful to see exactly how well uglify-js is performing but using 'gzip' will make the task take 5-10x longer to complete. Example output.

sourceMap

Type: Boolean
Default: false

If true, a source map file will be generated in the same directory as the dest file. By default it will have the same basename as the dest file, but with a .map extension.

sourceMapName

Type: String Function
Default: undefined

To customize the name or location of the generated source map, pass a string to indicate where to write the source map to. If a function is provided, the uglify destination is passed as the argument and the return value will be used as the file name.

sourceMapIn

Type: String Function
Default: undefined

The location of an input source map from an earlier compilation, e.g. from CoffeeScript. If a function is provided, the uglify source is passed as the argument and the return value will be used as the sourceMap name. This only makes sense when there's one source file.

sourceMap.includeSources

Type: Boolean
Default: false

Pass this flag if you want to include the content of source files in the source map as sourcesContent property.

sourceMap.root

Type: String
Default: undefined

With this option you can customize root URL that browser will use when looking for sources.

If the sources are not absolute URLs after prepending of the sourceMap.root, the sources are resolved relative to the source map.

sourceMap.url

Type: String
Default: undefined

Override the calculated value for sourceMappingURL in the source map. This is useful if the source map location is not relative to the base path of the minified file, i.e. when using a CDN

wrap

Type: String
Default: undefined

Wrap all of the code in a closure, an easy way to make sure nothing is leaking. For variables that need to be public exports and global variables are made available. The value of wrap is the global variable exports will be available as.

output.ascii_only

Type: Boolean
Default: false

Enables to encode non-ASCII characters as \uXXXX.

output.comments

Type: Boolean String Function
Default: undefined
Options: false 'all' 'some'

Turn on preservation of comments.

• false will strip all comments
• 'all' will preserve all comments in code blocks that have not been squashed or dropped
• 'some' will preserve all comments that include a closure compiler style directive (@preserve @license @cc_on)
• Function specify your own comment preservation function. You will be passed the current node and the current comment and are expected to return either true or false
• RegExp '/[RegExp]/' will preserve comments matching given RegExp or stringified RegExp

banner

Type: String
Default: ''

This string will be prepended to the minified output. Template strings (e.g. <%= config.value %>) will be expanded automatically.

footer

Type: String
Default: ''

This string will be appended to the minified output. Template strings (e.g. <%= config.value %>) will be expanded automatically.

ie8

Type: Boolean
Default: false

Set this to true if you still care about full compliance with Internet Explorer 6-8 quirks.

mangle.properties

Type: Boolean Object
Default: false

Turn on or off property mangling with default options. If an Object is specified, it is passed directly to ast.mangle_properties() (mimicking command line behavior). View all options here.

reserveDOMProperties

Type: Boolean
Default: false

Use this flag in conjunction with mangle.properties to prevent built-in browser object properties from being mangled.

exceptionsFiles

Type: Array
Default: []

Use this with mangle.properties to pass one or more JSON files containing a list of variables and object properties that should not be mangled. See the UglifyJS docs for more info on the file syntax.

nameCache

Type: String
Default: ''

A string that is a path to a JSON cache file that uglify will create and use to coordinate symbol mangling between multiple runs of uglify. Note: this generated file uses the same JSON format as the exceptionsFiles files.

output.quote_style

Type: Integer
Default: 0

Preserve or enforce quotation mark style.

• 0 will use single or double quotes such as to minimize the number of bytes (prefers double quotes when both will do)
• 1 will always use single quotes
• 2 will always use double quotes
• 3 will preserve original quotation marks

Usage examples

Basic compression

This configuration will compress and mangle the input files using the default options.

// Project configuration.
grunt.initConfig({
  uglify: {
    my_target: {
      files: {
        'dest/output.min.js': ['src/input1.js', 'src/input2.js']
      }
    }
  }
});

No mangling

Specify mangle: false to prevent changes to your variable and function names.

// Project configuration.
grunt.initConfig({
  uglify: {
    options: {
      mangle: false
    },
    my_target: {
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

Reserved identifiers

You can specify identifiers to leave untouched with an reserved array in the mangle options.

// Project configuration.
grunt.initConfig({
  uglify: {
    options: {
      mangle: {
        reserved: ['jQuery', 'Backbone']
      }
    },
    my_target: {
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

Source maps

Generate a source map by setting the sourceMap option to true. The generated source map will be in the same directory as the destination file. Its name will be the basename of the destination file with a .map extension. Override these defaults with the sourceMapName attribute.

// Project configuration.
grunt.initConfig({
  uglify: {
    my_target: {
      options: {
        sourceMap: true,
        sourceMapName: 'path/to/sourcemap.map'
      },
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

Advanced source maps

Set the sourceMap.includeSources option to true to embed your sources directly into the map. To include a source map from a previous compilation pass it as the value of the sourceMapIn option.

// Project configuration.
grunt.initConfig({
  uglify: {
    my_target: {
      options: {
        sourceMap: {
          includeSources: true
        },
        sourceMapIn: 'example/coffeescript-sourcemap.js', // input sourcemap from a previous compilation
      },
      files: {
        'dest/output.min.js': ['src/input.js'],
      },
    },
  },
});

Refer to the UglifyJS SourceMap Documentation for more information.

Turn off console warnings

Specify drop_console: true as part of the compress options to discard calls to console.* functions. This will suppress warning messages in the console.

// Project configuration.
grunt.initConfig({
  uglify: {
    options: {
      compress: {
        drop_console: true
      }
    },
    my_target: {
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

Beautify

Specify beautify: true to beautify your code for debugging/troubleshooting purposes. Pass an object to manually configure any other output options.

See UglifyJS documentation for more information.

// Project configuration.
grunt.initConfig({
  uglify: {
    my_target: {
      options: {
        beautify: true
      },
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    },
    my_advanced_target: {
      options: {
        beautify: {
          width: 80
        }
      },
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

Banner comments

In this example, running grunt uglify:my_target will prepend a banner created by interpolating the banner template string with the config object. Here, those properties are the values imported from the package.json file (which are available via the pkg config property) plus today's date.

Note: you don't have to use an external JSON file. It's also valid to create the pkg object inline in the config. That being said, if you already have a JSON file, you might as well reference it.

// Project configuration.
grunt.initConfig({
  pkg: grunt.file.readJSON('package.json'),
  uglify: {
    options: {
      banner: '/*! <%= pkg.name %> - v<%= pkg.version %> - ' +
        '<%= grunt.template.today("yyyy-mm-dd") %> */'
    },
    my_target: {
      files: {
        'dest/output.min.js': ['src/input.js']
      }
    }
  }
});

Conditional compilation

You can also enable UglifyJS conditional compilation. This is commonly used