This is a common pattern with jQuery extensions to ensure that they are always added to the jQuery object, but can be written using $ to keep the code tidy:
(function($){
$(function(){
// your code here
});
})(jQuery);
The $ would actually reference the jQuery library inside while still referring to Prototype on the outside! This can help tidy up your code
Source: javascript – Using Self Calling Anonymous Functions and $(document).ready – Stack Overflow