decimal.js for Rails 3.1+ asset pipeline.
decimal.js is "An arbitrary-precision Decimal type for JavaScript."
In your Gemfile, add this line:
gem "decimal-js-rails"
Then, run bundle install.
In your app/assets/javascripts/application.js, add this line:
//= require decimal
You're done!
decimal-rails-js 5.0.0 == decimal.js 5.0.0
The gem is available as open source under the terms of the MIT License.