A node.js module for compiling JavaScript code using Google Closure Compiler's REST API.
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A node.js module for compiling JavaScript code using Google Closure Compiler's REST API.

This library is also available as a Grunt plugin.

How to install

npm install gcc-rest

How to use

Basic example

Compile file1.js and file2.js and write it to compiled.js

var gcc = require('gcc-rest');
gcc.addFiles('/path/to/file1.js', '/path/to/file2.js');

If you're into chaining; this does the same:

   .addFiles('/path/to/file1.js', '/path/to/file2.js')

Note: Closing methods that perform compiling (output, compile and compilePassJson) cannot be chained.

An advanced example:

// Load gcc-rest module
var gcc = require('gcc-rest');

// Set Closure Compiler parameters
    output_info      : ['compiled_code', 'errors', 'warnings', 'statistics'],
    language         : 'ECMASCRIPT5_STRICT',
    compilation_level: 'ADVANCED_OPTIMIZATIONS',
    warning_level    : 'VERBOSE'

// Add files that should be compiled

// Replace code before compiling
gcc.replace(/'use strict';/g, '');

// Compile and write output to compiled.js,
// Handle errors when something goes wrong.
gcc.output('compiled/compiled.js', function(errorType, errorDetails) {
    console.error('Something went wrong:', errorType, errorDetails);

Adding code that should be compiled

Add a single file:


Add multiple files:

gcc.addFiles('/path/to/file1.js', '/path/to/file2.js', ...);

Add a directory of Javascript files:

// Use the optional second argument to pass an array of files
// that should be excluded when scanning the dir.
gcc.addDir('/path/to/dir', ['exclude1.js', 'exclude2.js']);

Manually add a snippet of Javascript:

gcc.addCode('alert("The crocodile must be green");');

Replace code before compiling:

gcc.replace(/"console\.log\(.*\);"/g, ''); // Removes all console.log statements

Compiler request parameters

Documentation on Google Closure Compiler's request parameters can be found here. The additional web service options are also supported. Unsupported parameters will print a warning. gcc-rest does not overwrite Google Closure Compiler's default settings.

Set a Google Closure Compiler request parameter:

gcc.param('warning_level', 'VERBOSE');

Or set multiple request parameters at once:

    language                  : 'ECMASCRIPT5_STRICT',
    warning_level             : 'VERBOSE',
    use_types_for_optimization: 'true'

Handling the compiled output

Output to a file:


You may also pass the compiled source to a callback function. The compiled source is passed as the first parameter.

Use a callback function by supplying a function reference:


Or an anonymous function:

gcc.compile(function(compiledStr) {
    require('fs').writeFile('path/to/myfile.js', compiledStr);

Access the unmodified Json response from Google Closure Compiler by calling compilePassJson():

gcc.compilePassJson(function(json) {
    // json contains objects like compiledCode, errors, warnings, statistics
    // see output_format > json at https://developers.google.com/closure/compiler/docs/api-ref

Prepend the compiled source with a header:

gcc.header('// This file was compiled using Google Closure Compiler\n');

Handling errors

Handle errors by supplying an error handling function to the second argument of output, compile or compilePassJson. This function will be called when something goes wrong. The error handling function accepts two parameters, errorType and errorDetails.

errorType provides on of these error types:

  • service_error: The Google Closure Compiler REST API could not process the request. Check the compiler docs for details..
  • request_error: The HTTP request could not be sent to the API.
  • server_error: The HTTP response did not return a 200: Success status. Please note that the API will return a 200: Success when a service_error occurs.

errorDetails provides (unstructured) detailed information.


gcc.output('/path/to/compiled.js', function(errorType, errorDetails) {
    // Error handling code

gcc.compile(function(compiledStr) {
    // Compiled string handling code
}, function(errorType, errorDetails) {
    // Error handling code

gcc.compilePassJson(function(json) {
    // Json handling code
}, function(errorType, errorDetails) {
    // Error handling code

Custom logging

By default, gcc-rest uses the console object for logging. If you want, you can overwrite gcc.console.info, gcc.console.warn and gcc.console.error with your own functions. Example:

gcc.console.error = function() {
    fs.appendFile('error.log', arguments.join(', '));

Unit testing

  1. Clone from GitHub
  2. Run npm install to install the Mocha test framework
  3. Run npm test

Update history

  • 2014-03-06: v0.2.5 Provider better error handling functionality documentation
  • 2014-03-06: v0.2.4 Provider better error handling functionality
  • 2013-12-01: v0.2.3 Consistency in error/warning logging
  • 2013-08-08: v0.2.0 Add tests, travis, allow overwriting console
  • 2013-04-07: v0.1.6 Allow chaining after the addDir method
  • 2013-02-02: v0.1.5 Add addDir method
  • 2013-01-12: v0.1.4 Fix issue where no header prepends "undefined" to output
  • 2013-01-05: v0.1.3 Add support for debug parameter
  • 2012-12-30: v0.1.2 Add support for use_types_for_optimization parameter
  • 2012-10-02: v0.0.3 Prevent module cache
  • 2012-10-02: v0.0.1 Initial release


gcc-rest is released under the MIT License.