Question

In the file application.html.erb, I see the line

  <%= javascript_include_tag :defaults %>

What does :defaults mean here? What Javascript files does it include?

Answer 1

To include the Prototype and Scriptaculous javascript libraries in
your application, pass :defaults as the source. When using :defaults,
if an application.js file exists in your public javascripts directory,
it will be included as well.

Source

In other words:

• prototype.js
• controls.js
• dragdrop.js
• effects.js
• rails.js (this one is not listed in the API, but it is included)
• application.js if it exists