Question

How do I explain the role of the arguments passed in the beginning vs end of a wrapped Javascript closure as the one shown below?

(function($, window) {
  return $(function() {
    return alert("js!");
  });
})($, window);

Answer 1

The first appearance are function parameters, the second is passing values for those parameters when executing the function.

Keep in mind, the parameters to the function don’t need to match the names being passed (this could, in fact, cause confusion later on):

(function(jQuery, w) {
    return jQuery(function(){
        return alert("js!");
    });
})($, window);

Would work the same way.