grunt-closure-compiler

A Grunt task for Closure Compiler.

Getting Started

First you need to download a build of Closure Compiler or build it from the source (see details below).

Optionally, you can set up an environment variable called CLOSURE_PATH that points to your Closure Compiler dir (see details below).

Install this module on your project's grunt.js gruntfile:

$ npm install grunt-closure-compiler

Then register the task by adding the following line to your grunt.js gruntfile:

grunt.loadNpmTasks('grunt-closure-compiler');

Then you can minify JavaScript calling:

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      closurePath: '/src/to/closure-compiler',
      js: 'static/src/frontend.js',
      jsOutputFile: 'static/js/frontend.min.js',
      maxBuffer: 500,
      options: {
        compilation_level: 'ADVANCED_OPTIMIZATIONS',
        language_in: 'ECMASCRIPT5_STRICT'
      }
    }
  }
});

closurePath is required if you choose not to set up the CLOSURE_PATH environment variable. In this case, it should point to the install dir of Closure Compiler (not the subdirectory where the compiler.jar file is located).

js property is always required.

If jsOutputFile property is set, the script will be minified and saved to the file specified. Otherwise it will be output to the command line.

maxBuffer property

If the buffer returned by closure compiler is more than 200kb, you will get an error saying "maxBuffer exceeded". To prevent this, you can set the maxBuffer to the preffered size you want (in kb)

Use cwd to specify the working directory where closure compiler is called. Useful in when you want to process common js modules.

Optionally, several parameters can be passed to options object.

Documentation

Closure Compiler installation from source

Install dependencies:

$ sudo apt-get install git ant openjdk-7-jdk

Then checkout the source from Git and build:

$ git clone https://code.google.com/p/closure-compiler/
$ cd closure-compiler
$ ant

To refresh your build, simply call:

$ git pull
$ ant clean
$ ant

Mac

Mac users can install it from brew:

$ brew install closure-compiler

Set up the environment variable

Setting up a CLOSURE_PATH environment variable is preferred because:

• You don't have to specify the closurePath each time.
• It makes it easy to use contributed externs.

In case you're wondering, Closure Compiler utilizes continuous integration, so it's unlikely to break.

If you create the CLOSURE_PATH environment variable, make sure to have it pointing to the closure-compiler dir created earlier (and not to the build subdirectory where the jar is located).

Mac

On Mac, when installed with brew, you can get the install path using:

$ brew --prefix closure-compiler
/usr/local/Cellar/closure-compiler/20120710

Just append /libexec to what you get. In this example, you should use the following path:

/usr/local/Cellar/closure-compiler/20120710/libexec/

Minification report

By default, a report file is generated next to the built file.

You can specify the path and name where the report will be saved using the reportFile property.

To deactivate report creation, set noreport to true.

js property

This task is a multi task, you can specify several targets. The task can minify many scripts at a time.

js can be an array if you need to concatenate several files to a target.

You can use Grunt <%= somePropInitConfig.sub.sub.prop %> or * based syntax to have the file list expanded:

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      js: 'static/src/frontend.js',
      jsOutputFile: 'static/js/frontend.min.js',
    },
    frontend_debug: {
      js: [
        '<%= closure-compiler.frontend.js %>',
        // Will expand to 'static/src/frontend.js'
        'static/src/debug.*.js'
        // Will expand to 'static/src/debug.api.js',
        //   'static/src/debug.console.js'...
      ],
      jsOutputFile: 'static/js/frontend.debug.js',
      options: {
        debug: true,
        formatting: 'PRETTY_PRINT'
      }
    },
  }
});

options properties

Properties in options are mapped to Closure Compiler command line. Just pass options as a map of option-value.

If you need to pass the same options several times, make it an array. See define below:

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      js: 'static/src/frontend.js',
      jsOutputFile: 'static/js/frontend.min.js',
      options: {
        compilation_level: 'ADVANCED_OPTIMIZATIONS',
        language_in: 'ECMASCRIPT5_STRICT',
        define: [
          '"DEBUG=false"',
          '"UI_DELAY=500"'
        ],
      }
    }
  }
});

When defining externs, if you added the CLOSURE_PATH environment variable you can easily reference Closure Compiler builtin externs using <%= process.env.CLOSURE_PATH %> Grunt template:

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      js: 'static/src/frontend.js',
      jsOutputFile: 'static/js/frontend.min.js',
      options: {
        externs: '<%= process.env.CLOSURE_PATH %>/contrib/externs/jquery-1.7.js',
      }
    }
  }
});

Otherwise, use the <%= %> Grunt template:

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      closurePath: '/src/to/closure-compiler',
      js: 'static/src/frontend.js',
      jsOutputFile: 'static/js/frontend.min.js',
      options: {
        externs: '<%= closure-compiler.frontend.closurePath %>/contrib/externs/jquery-1.7.js'
      }
    }
  }
});

To specify boolean options (such as process_common_js_modules, i.e. no value are required), set its value to undefined (or null):

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      js: 'static/src/frontend.js',
      jsOutputFile: 'static/js/frontend.min.js',
      options: {
        process_common_js_modules: undefined,
        common_js_entry_module: 'exports'
      }
    }
  }
});

For automatic resolving common js modules you can use

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      cwd: 'static/src/'
      js: '*.js',
      jsOutputFile: 'static/js/frontend.min.js',
      options: {
        common_js_entry_module: 'frontend.js',
        transform_amd_modules: undefined,
        process_common_js_modules: undefined
      }
    }
  }
});

Module Code Splitting

Closure Compiler can split the output of a compilation into multiple files to support dynamic loading. This process uses the --chunk flag (before June 2018 it was named --module). See how do I split my javascript into modules

Modules can be stitched together without a module loading logic enabling to achieve optimal compression and optimization with the ability to load modules selectively.

Source: https://github.com/google/closure-compiler/wiki/JS-Modules#code-splitting-output-modules

grunt.initConfig({
  'closure-compiler': {
    frontend: {
      closurePath: '/src/to/closure-compiler',
      modules: {
        "module-name": {
          src: ['js/source.js', 'js/other-source.js']
        },
        "extra-module": {
          src: ['js/extra-module.js'],
          dep: ['module-name']
        }
      },
      moduleOutputPath: 'static/js/',
      maxBuffer: 500,
      options: {
        compilation_level: 'ADVANCED_OPTIMIZATIONS',
        language_in: 'ECMASCRIPT5_STRICT'
      }
    }
  }
});

Note

grunt-closure-compiler initial development was founded by Dijiwan.

The directory structure was inspired by grunt-less, a Grunt task for Less.

License

Copyright (c) 2013 Guillaume Marty

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.