Question

I am too curious to know the difference between $ and $.fn? Can anyone please explain this to me in details? Also what is $.fn?

Answer 1

$ is a function (specifically, a variable pointing to the jQuery function — an alias). $.fn is a property on that function, which points to the prototype of the internal init function jQuery uses to create instances, as we can see in the jQuery code:

jQuery.fn.init.prototype = jQuery.fn;

(That’s line 289 of the current un-minified jQuery file, v1.8.3.)

$.fn is there so that it’s easy to add properties to it. When you create jQuery objects, they have those properties, because of JavaScript’s prototypical inheritance. The most common properties to add to it are, of course, functions that do things (jQuery plug-ins).