This Ruby gem patches ActionView to add the js_include method to your views. The difference between js_include and the default javascript_include_tag is that the latter will re-include Javascript that has already been included on the same page. js_include was created to allow for a convenient means of being assured that a single Javascript source file will be included only once, regardless of how many times it may times js_include might have been called on it.

The primary use case of js_include is in partials. In the case where a partial requires it's own collection of Javascript it, the partial template can easily js_include whichever source files it needs. If the parent template also js_include the same same file, js_include will just do "the right thing"

To get started, you will need to include the js_include gem in your project. Simply edit your Gemfile to include the line:

gem "js_include", "~> 0.9.5"

Once completed, do not forget to run bundle install, and you are off to the races.

From your views you can now use js_include wherever you previously have used javascript_include_tag.

<%= js_include 'jquery' %>