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A CommonJS module implementation in Ruby for client-side JavaScript
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modulr is a CommonJS module implementation in Ruby for client-side JavaScript. It accepts a singular file as input (the program) on which is does static analysis to recursively resolve its dependencies.

The program, its dependencies and a small, namespaced JavaScript library are concatenated into a single js file with optional minification through the YUI Compressor. This improves load times by minimizing HTTP requests. Further load time performance improvements are made possible by the built-in lazy evaluation option. Modules are delivered as JavaScript strings--instead of functions--and are evaluated only when required.

The bundled JavaScript library provides each module with the necessary require function and exports and module free variables. In its full version, the bundled library also provided support for the require.ensure (async module requires) and require.define (module transport) methods.

modulr can also be used as a build tool for JavaScript code that will be executed in a regular JS environment. In this case, the global variable defined by the --global-export option is assigned the exports of the main CommonJS module and asynchronous module requires are not supported.

Finally, modulr allows you to create handy dependency graphs.


$ [sudo] gem install modulr


modulr is available as a Ruby library or as a command-line utility (modulrize).

To process a JavaScript source file, just run:

$ modulrize filename.js > output.js

You can also simultaneously process multiples files like so:

$ modulrize filename.js other_filename.js > output.js

Options are as follows:

-o, --output=FILE                Write the output to FILE. Defaults to stdout.
-r, --root=DIR                   Set DIR as root directory. Defaults to the directory containing FILE.
    --lazy-eval [MODULES]        Enable lazy evaluation of all JS modules or of those specified by MODULES.
                                 MODULES accepts a comma-separated list of identifiers.
    --minify                     Minify output using YUI Compressor.
    --global-export[=GLOBAL_VAR] If GLOBAL_VAR is specified and only one module is being processed, exports it to the GLOBAL_VAR global variable.
                                 If GLOBAL_VAR is specified and multiple modules are being processed, exports each one of them as a property of GLOBAL_VAR.
                                 If GLOBAL_VAR isn't specified, exports the module to global variables corresponding to their identifier.
    --main-module=MAIN_MODULE    Set the identifier of the main module (available through `require.main`).
    --sync                       Load all dependencies synchronously.
    --dependency-graph[=OUTPUT]  Create a dependency graph of the module.
-h, --help                       Show this message.

Minification options (these are forwarded to YUI Compressor without the "minify-" prefix):

--minify-disable-optimizations   Disable all micro optimizations.
--minify-nomunge                 Minify only, do not obfuscate.
--minify-verbose                 Display informational messages and warnings.
--minify-line-break COLUMN       Insert a line break after the specified column number.
--minify-preserve-semi           Preserve all semicolons.


To run the specs, first clone the Git repository then grab the CommonJS specs, included as a Git submodule, by running:

$ git clone git://
$ cd modulr
$ git submodule init
$ git submodule update

Mozilla's SpiderMonkey is required and the js command line executable must be available on the load path (try which js).

You can run all the specs by issuing:

$ rake spec

Alternatively, a list of comma-separated specs can be specified through the SPECS environment variable (see vendor/commonjs/tests/modules/1.0) for a comprehensive list of available specs).

$ rake spec SPECS=absolute,transitive
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