google-closure-compiler

google-closure-compiler

Check, compile, optimize and compress Javascript with Closure-Compiler

This repository tracks issues related to the publication to npmjs.org and associated plugins. Any bugs not related to the plugins themselves should be reported to the main repository.

Getting Started

This package requires java to be installed and in the path. Looking for a version that does not require java? See google-closure-compiler-js.

If you are new to Closure-Compiler, make sure to read and understand the compilation levels as the compiler works very differently depending on the compilation level selected.

For help or questions with the compiler, the best resource is Stack Overflow. Posts there are monitored by multiple Closure Compiler team members.

You may also post in the Closure Compiler Discuss Google Group.

Please don't cross post to both Stackoverflow and Closure Compiler Discuss.

Usage

The simplest way to invoke the compiler (e.g. if you're just trying it out) is with npx:

npx google-closure-compiler --js=my_program.js --js_output_file=out.js

The compiler package also includes build tool plugins for Grunt and Gulp. There is also an official webpack plugin.

Installation

npm install --save google-closure-compiler

Configuration

The compiler has a large number of flags. The best documentation for the flags can be found by running the --help command of the compiler.jar found inside the node_modules/google-closure-compiler folder:

java -jar compiler.jar --help

Specifying Options

Both the grunt and gulp tasks take options objects. The option parameters map directly to the compiler flags without the leading '--' characters.

Values are either strings or booleans. Options which have multiple values can be arrays.

  {
    js: ['/file-one.js', '/file-two.js'],
    compilation_level: 'ADVANCED',
    js_output_file: 'out.js',
    debug: true
  }

For advanced usages, the options may be specified as an array of strings. These values include the "--" characters and are directly passed to the compiler in the order specified:

  [
    '--js', '/file-one.js',
    '--js', '/file-two.js',
    '--compilation_level', 'ADVANCED',
    '--js_output_file', 'out.js',
    '--debug'
  ]

When an array of flags is passed, the input files should not be specified via the build tools, but rather as compilation flags directly.

Some shells (particularly windows) try to do expansion on globs rather than passing the string on to the compiler. To prevent this it is necessary to quote certain arguments:

  {
    js: '"my/quoted/glob/**.js"',
    compilation_level: 'ADVANCED',
    js_output_file: 'out.js',
    debug: true
  }

Using the Grunt Task

Include the plugin in your Gruntfile.js:

require('google-closure-compiler').grunt(grunt);
// The load-grunt-tasks plugin won't automatically load closure-compiler

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

Basic Configuration Example:

require('google-closure-compiler').grunt(grunt);

// Project configuration.
grunt.initConfig({
  'closure-compiler': {
    my_target: {
      files: {
        'dest/output.min.js': ['src/js/**/*.js']
      },
      options: {
        compilation_level: 'SIMPLE',
        language_in: 'ECMASCRIPT5_STRICT',
        create_source_map: 'dest/output.min.js.map',
        output_wrapper: '(function(){\n%output%\n}).call(this)\n//# sourceMappingURL=output.min.js.map'
      }
    }
  }
});

Closure Library Example:

var compilerPackage = require('google-closure-compiler');
compilerPackage.grunt(grunt);

// Project configuration.
grunt.initConfig({
  'closure-compiler': {
    my_target: {
      files: {
        'dest/output.min.js': ['src/js/**/*.js']
      },
      options: {
        js: '/node_modules/google-closure-library/**.js'
        externs: compilerPackage.compiler.CONTRIB_PATH + '/externs/jquery-1.9.js',
        compilation_level: 'SIMPLE',
        manage_closure_dependencies: true,
        language_in: 'ECMASCRIPT5_STRICT',
        create_source_map: 'dest/output.min.js.map',
        output_wrapper: '(function(){\n%output%\n}).call(this)\n//# sourceMappingURL=output.min.js.map'
      }
    }
  }
});

Advanced Usage with Arguments Array:

// Project configuration.
grunt.initConfig({
  'closure-compiler': {
    my_target: {
      options: {
        // When args is present, all other options are ignored
        args: [
          '--js', '/file-one.js',
          '--js', '/file-two.js',
          '--compilation_level', 'ADVANCED',
          '--js_output_file', 'out.js',
          '--debug'
        ]
      }
    }
  }
});

Using the Gulp Plugin

The gulp plugin supports piping multiple files through the compiler.

Options are a direct match to the compiler flags without the leading "--".

Basic Configuration Example:

var closureCompiler = require('google-closure-compiler').gulp();

gulp.task('js-compile', function () {
  return gulp.src('./src/js/**/*.js', {base: './'})
      .pipe(closureCompiler({
          compilation_level: 'SIMPLE',
          warning_level: 'VERBOSE',
          language_in: 'ECMASCRIPT6_STRICT',
          language_out: 'ECMASCRIPT5_STRICT',
          output_wrapper: '(function(){\n%output%\n}).call(this)',
          js_output_file: 'output.min.js'
        }))
      .pipe(gulp.dest('./dist/js'));
});

Use without gulp.src

Gulp files are all read into memory, transformed into a JSON stream, and piped through the compiler. With large source sets this may require a large amount of memory.

Closure-compiler can natively expand file globs which will greatly alleviate this issue.

var compilerPackage = require('google-closure-compiler');
var closureCompiler = compilerPackage.gulp();

gulp.task('js-compile', function () {
  return closureCompiler({
        js: './src/js/**.js',
        externs: compilerPackage.compiler.CONTRIB_PATH + '/externs/jquery-1.9.js',
        compilation_level: 'SIMPLE',
        warning_level: 'VERBOSE',
        language_in: 'ECMASCRIPT6_STRICT',
        language_out: 'ECMASCRIPT5_STRICT',
        output_wrapper: '(function(){\n%output%\n}).call(this)',
        js_output_file: 'output.min.js'
      })
      .src() // needed to force the plugin to run without gulp.src
      .pipe(gulp.dest('./dist/js'));
});

gulp.src base option

Gulp attempts to set the base of a glob from the point of the first wildcard. This isn't always what is desired. Users can specify the { base: 'path' } option to gulp.src calls to override this behavior.

Advanced Usage with Arguments Array:

var closureCompiler = require('google-closure-compiler').gulp();

gulp.task('js-compile', function () {
  return closureCompiler([
        '--js', '/file-one.js',
        '--js', '/file-two.js',
        '--compilation_level', 'ADVANCED',
        '--js_output_file', 'out.js',
        '--debug'
      ])
      .src() // needed to force the plugin to run without gulp.src
      .pipe(gulp.dest('./dist/js'));
});

Gulp Sourcemaps

The gulp plugin supports gulp sourcemaps.

var closureCompiler = require('google-closure-compiler').gulp();
var sourcemaps = require('gulp-sourcemaps');

gulp.task('js-compile', function () {
  return gulp.src('./src/js/**/*.js', {base: './'})
      .pipe(sourcemaps.init())
      .pipe(closureCompiler({
          compilation_level: 'SIMPLE',
          warning_level: 'VERBOSE',
          language_in: 'ECMASCRIPT6_STRICT',
          language_out: 'ECMASCRIPT5_STRICT',
          output_wrapper: '(function(){\n%output%\n}).call(this)',
          js_output_file: 'output.min.js'
        }))
      .pipe(sourcemaps.write('/')) // gulp-sourcemaps automatically adds the sourcemap url comment
      .pipe(gulp.dest('./dist/js'));
});

Running the compiler using nailgun

This gets around the long startup time of Google Closure Compiler using Nailgun, which runs a single java process in the background and keeps all of the classes loaded.

First you need to install closure-gun by running the following command.

npm install closure-gun

Gulp

var compilerPackage = require('google-closure-compiler');
var closureCompiler = compilerPackage.gulp();

compilerPackage.compiler.JAR_PATH = undefined;
compilerPackage.compiler.prototype.javaPath = './node_modules/.bin/closure-gun'

Note that when using gulp, Only without gulp.src works with nailgun.

Grunt

var compilerPackage = require('google-closure-compiler');
var closureCompiler = compilerPackage.grunt();

compilerPackage.compiler.JAR_PATH = undefined;
compilerPackage.compiler.prototype.javaPath = './node_modules/.bin/closure-gun'

Specifying Extra Java Arguments

Some users may wish to pass the java vm extra arguments - such as to specify the amount of memory the compiler should be allocated. Both the grunt and gulp plugins support this.

Grunt

require('google-closure-compiler').grunt(grunt, ['-Xms2048m']);

Gulp

var closureCompiler = require('google-closure-compiler').gulp({
  extraArguments: ['-Xms2048m']
});

Native Node Usage (for Plugin Authors)

A low-level node class is included to facilitate spawning the compiler jar as a process from Node. In addition, it exposes a static property with the path to the compiler jar file.

var ClosureCompiler = require('google-closure-compiler').compiler;

console.log(ClosureCompiler.COMPILER_PATH); // absolute path the compiler jar
console.log(ClosureCompiler.CONTRIB_PATH); // absolute path the contrib folder which contains

var closureCompiler = new ClosureCompiler({
  js: 'file-one.js',
  compilation_level: 'ADVANCED'
});

var compilerProcess = closureCompiler.run(function(exitCode, stdOut, stdErr) {
  //compilation complete
});

License

Copyright 2015 The Closure Compiler Authors

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Version History

Closure Compiler release notes can be found on the main repository wiki.