Bundle and minify JavaScript projects
Ruby JavaScript
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Ruby utility to help in developing JavaScript libraries. Lets you declare JavaScript libraries composed of multiple files. Easily bundle and minify your JavaScript bundles when you're done. Includes a Rack server for easy testing.


JBundle is a Ruby gem.

gem install jbundle


Define a set of javascript files to bundle and minify

JBundle.config do
  version '1.6.1'

  src_dir File.dirname(__FILE__) + '/src'

  bundle 'foo.js' do
    file 'file1.js'
    file 'file2.js'

  bundle 'foo2.js' do
    file 'file3.js'
    file 'file4.js'

  file 'file4.js'

  file 'text.txt'

  # Filters can be use for string substitution
  filter do |src, config|
    src.gsub(/<VERSION>/, config.version)

  target_dir 'dist'


Then write them to the configured target directory


JBundle.write! returns an array of paths of all files written.

This will write the following files:



Or you can build a single bundle/file dynamically (ie. for testing, or for serving and caching on first serve)

JBundle.config_from_file './JFile'


JBundle.config_from_file './JFile'

You can bundle licenses in bundles. Licenses will not be minified even though they end up being part of minified files

bundle 'foo2.js' do
  license 'license.txt'
  file 'file3.js'
  file 'file4.js'

All defined filters will run on the src for all these cases.

Versioned file names, jQuery style

All of the examples above bundle to versioned directories in the "dist" directory. If you want jQuery-style file names, where there's no version directory and the version number is part of the file name, you can do this:

version '1.6.1', :directory => false

bundle 'foo.js' => 'foo2-[:version].js' do
  license 'license.txt'
  file 'file3.js'
  file 'file4.js'

That will produce:


That works for single-file libraries too:

file 'jquery.lightbox.js' => 'jquery.lightbox-[:version].js'


You can filter both minified and un-minified source and license content with the filter method

# Filters can be use for string substitution
filter do |src, config|
  src.gsub(/<VERSION>/, config.version)

You can declare filters that run on un-minified output only

filter :src do |src, config|
  src.gsub(/<SRC_MODE>/, 'full source')

... And minified output only

filter :min do |src, config|
  src.gsub(/<SRC_MODE>/, 'minified source')

All filters must return a copy of the source, so use src.gsub instead of src.gsub!


You can add configuration in a JFile in the root of your project.

version '1.0.1'

src_dir './'

bundle 'foo.js' do
  license 'license.txt'
  file 'file1.js'
  file 'file2.js'

file 'page.html'

filter do |src, config|
  src.gsub! /<VERSION>/, config.version.to_s

target_dir 'dist'

Then you can bundle everything up with the command line tool

$ jbundle

You can run arbitrary code after writing all versioned files by registering an after_write block in your JFile. The following example copies a .swf file from the src dir to all versioned directories

after_write do |config|

  config.version.releaseable.each do |version|
    from = "#{config.src_dir}/foo.swf"
    to = "#{config.target_dir}/#{version}/foo.swf"
    puts "copying #{to}"
    FileUtils.cp(from, to)


config.version.releaseble returns an array with with all created versions (ie. ['1.6.1', '1.6'] or just ['1.6.1-pre'] for prereleases).

Files in subdirectories in the src directory will keep the local directory tree, so

file 'foo/text.txt'

Ends up as ./dist/1.6/foo/text.txt and ./dist/1.6.1/foo/text.txt

You can also copy to a different file name in the target directory using hash notation

file 'foo/text.txt' => 'bar.txt'


If you want a prerelease not to overwrite the previous point release, suffix it with "-pre", as in:

version '1.0.1-pre'

Test server

JBundle command-line comes with a built-in Rack server that makes it easy to test you JavaScript bundles as you develop them.

jbundle server

Starting test server on http://localhost:5555. Available bundles:
- /foo.js
Run tests on ./tests/index.html

That serves JavaScript bundles defined in your JFile in port 5555. Pass the -p option for a different port. ./tests/index.html runs your tests (Qunit by default) in the ./tests directory

You can chose what testing framework to use when initialising the project. Options are qunit and jasmine.

jbundle init foo.js --tests=jasmine

Learn more about the JBundle command-line with

jbundle help # all commands
jbundle help server # server command options


The command line has a quick generator that creates stub files for your library code, an example file and tests using Qunit.

jbundle init my_library.js

create  JFile
      create  src
      create  src/license.txt
      create  src/my_library.js
      create  test
      create  test/index.html
      create  test/tests.js
      create  test/qunit.js
      create  test/qunit.css
      create  dist
Done. Try it!

    jbundle s
    open test/index.html

At the moment only Qunit (default) and Jasmine are supported in the generator but others would be easy to add.

To generate jasmine test stubs, run the command with -t jasmine

If you don't need the test stubs run the command with --no-tests


  • DRY up stuff, better error handling for missing config