Rails 3 - how to defer parsing of JavaScript

I am trying to optimize my website and one of the suggestions I got was
to defer parsing of JavaScript. I have googled it for a couple of hours
but I haven't come across an elegant solution to do this in Rails 3. I
am using the standard

<%= javascript_include_tag :application -%>

tag in my code, just before the closing head tag. Does anybody know a
relatively simple way to defer the loading of all the Javascript of the
application.js file? Thanks.

Hi Geoffrey,

I am going to try it out and see whether or not Google considers this as
being deferred.

Kind regards,