Opal is a Ruby to JavaScript compiler. It is source-to-source, making it fast as a runtime. Opal includes a compiler (which can be run in any browser), a corelib and runtime implementation. The corelib/runtime is also very small.

Sprockets is a Rack-based asset packaging system that concatenates and serves JavaScript, CoffeeScript, CSS, Sass, and SCSS.

Use webpack to manage app-like JavaScript modules in Rails

Rails bindings for opal JS engine

Uglifier minifies JavaScript files by wrapping UglifyJS to be accessible in Ruby

If you need to send some data to your js files and you don't want to do this with long way trough views and parsing - use this force!

Page-specific javascript for Rails done right

jQuery CDN script tags and fallback in one neat package. Current version is for jQuery v2.1.0

Keep your vendor files up to date

Rack middleware that executes javascript before serving pages to crawlers.

Auto-magical scaffolding for Paul Irish's DOM-based Routing way of organizing your javascript.

Mousetrap is a javascript library for handling keyboard shortcuts in your web applications. This gem integrates Mousetrap with Rails asset pipeline for easy of use.

Wiselinks makes following links and submitting some forms in your web application smarter and faster

Better Unobtrusive JavaScript Respond

A light wrapper for using dynamo.js with Ruby on Rails

Auto-magical scaffolding for the Garber-Irish Implementation way of organizing your javascript.

Resolve dependencies, merge and minify CSS and JavaScript files with Juicer - the command line tool for frontend engineers

Ruby version of Dean Edwards' JavaScript compressor

Barista provides simple, integrated support for CoffeeScript in Rack and Rails applications. Much like Compass does for Sass, It also provides Frameworks (bundleable code which can be shared via Gems). Lastly, it also provides a Rack Application (which can be used to server compiled code), a ar...

A rake task to minify javascripts and coffeescripts

Build tools for JavaScript projects

Stupidly simple command line tool for squashing JS and CSS files. Used mostly for building UserJS

Inspiredby HAML, SASS and JABL by mr Hampton Catlin

JavaScript/CSS/HTML sources compiler

Ruby CoffeeScript is a bridge to the JS CoffeeScript compiler.