Narnia's Psychedelic Mushrooms


    20170910.0.1 • Public • Published


    This is a (hopefully temporary) fork of closure-compiler-js that points to my fork of closure-compiler.

    It only includes this change:



    Check, compile, transpile, optimize and compress JavaScript with Closure Compiler in JS.

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

    Unlike other packages, this allows Closure Compiler to run entirely in JS. Java is not required.

    This is an experimental release - meaning some features are not available and performance may not be on-par with the Java implementation - details here.


    First, install the latest version:

    yarn add google-closure-compiler-js  # or
    npm install --save google-closure-compiler-js

    The module supports modern web browsers as well as Node v4 LTS, and provides compile as a low-level method to compile JavaScript. By default, this compiles ES6 to ES5 and includes the default set of ECMAScript externs files. For example:

    const compile = require('google-closure-compiler-js').compile;
    const flags = {
      jsCode: [{src: 'const x = 1 + 2;'}],
    const out = compile(flags);;  // will print 'var x = 3;\n'

    Or to install the command-line version, do:

    npm install -g google-closure-compiler-js

    You should now be able to run google-closure-compiler-js as a command. The google-closure-compiler-js command can read from stdin or from a file. For example:

    google-closure-compiler-js code.js > minified.js

    Run google-closure-compiler-js --help for full usage information.

    Build Systems


    Your webpack.config.js should look like this:

    const ClosureCompiler = require('google-closure-compiler-js').webpack;
    const path = require('path');
    module.exports = {
      entry: [
        path.join(__dirname, 'app.js')
      output: {
        path: path.join(__dirname, 'dist'),
        filename: 'app.min.js'
      plugins: [
        new ClosureCompiler({
          options: {
            languageIn: 'ECMASCRIPT6',
            languageOut: 'ECMASCRIPT5',
            compilationLevel: 'ADVANCED',
            warningLevel: 'VERBOSE',


    Your gulpfile.js should contain a task like this:

    const compiler = require('google-closure-compiler-js').gulp();
    gulp.task('script', function() {
      return gulp.src('./path/to/src.js', {base: './'})
          // your other steps here
              compilationLevel: 'SIMPLE',
              warningLevel: 'VERBOSE',
              outputWrapper: '(function(){\n%output%\n}).call(this)',
              jsOutputFile: 'output.min.js',  // outputs single file
              createSourceMap: true,


    Flag Default Usage
    angularPass false Generate $inject properties for AngularJS for functions annotated with @ngInject
    applyInputSourceMaps true Compose input source maps into output source map
    assumeFunctionWrapper false Enable additional optimizations based on the assumption that the output will be wrapped with a function wrapper. This flag is used to indicate that "global" declarations will not actually be global but instead isolated to the compilation unit. This enables additional optimizations.
    checksOnly false Don't generate output. Run checks, but no optimization passes.
    compilationLevel SIMPLE Specifies the compilation level to use.
    dartPass false
    defines null Overrides the value of variables annotated with @define, an object mapping names to primitive types
    env BROWSER Determines the set of builtin externs to load.
    Options: BROWSER, CUSTOM
    exportLocalPropertyDefinitions false
    generateExports false Generates export code for those marked with @export.
    languageIn ES6 Sets what language spec that input sources conform to.
    languageOut ES5 Sets what language spec the output should conform to.
    newTypeInf false Checks for type errors using the new type inference algorithm.
    outputWrapper null Interpolate output into this string, replacing the token %output%
    polymerVersion null Specify the Polymer version pass to use.
    preserveTypeAnnotations false
    processCommonJsModules false Process CommonJS modules to a concatenable form, i.e., support require statements.
    renamePrefixNamespace Specifies the name of an object that will be used to store all non-extern globals.
    rewritePolyfills false Rewrite ES6 library calls to use polyfills provided by the compiler's runtime.
    useTypesForOptimization false Enable or disable the optimizations based on available type information. Inaccurate type annotations may result in incorrect results.
    warningLevel DEFAULT Specifies the warning level to use.
    jsCode [] Specifies the source code to compile.
    externs [] Additional externs to use for this compile.
    createSourceMap false Generates a source map mapping the generated source file back to its original sources.


    The Closure Compiler supports the following languages:

    • ECMASCRIPT6_TYPED (experimental)
    • ECMASCRIPT_2017 (experimental)

    Source Code

    Unless you're using Gulp's or Webpack's plugins, you'll need to specify code via flags:

    • Both jsCode and externs accept an array containing objects in the form {src, path, sourceMap}.
    • Using path you can construct a virtual filesystem for use with ES6 or CommonJS imports — although for CommonJS you'll have to set processCommonJsModules: true.


    The JavaScript version of the Closure-Compiler is transpiled by GWT from the Java source. For more details on the differences in behavior see the super sourced files in the main repository.

    Version History

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


    Copyright © 2017 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

    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.


    npm i @gaearon/google-closure-compiler-js

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