rails.js's purpose

Question

I am getting acquainted with Rails 3, UJS and JQuery. I understand why jquery.js and application.js are needed but why is rails.js needed?

Answer 1

Think of it as the missing link between jQuery and Rails. Suppose you have a form tag,

<form method="POST" action="/some/path" data-remote="true">
  ..
</form>

The code that will look at the data-remote on this form tag and other such attributes used that Rails looks at, and submit this form through AJAX is handled by rails.js. It is like a connector between Rails and jQuery. The source is rather simple which you can read at https://github.com/rails/jquery-ujs/blob/master/src/rails.js