Question

I am reading up on creating custom jQuery plugins and am a little confused as to the meaning of the following syntax:

(function($){  
    $.fn.truncate = function() {  
        return this.each(function() { 
        });
     };
})(jQuery);

I understand that function($) is an anonymous function that accepts the $. I just don’t quite understand why this function is wrapped in brackets and how the following sets of brackets with jQuery in them…work.

Answer 1

It is not safe to assume that $ is owned by the jQuery library. Some other javascript libraries/users may/do use that identifier for other purposes. However, jQuery is always the jQuery library (barring any evildoers).

This anonymous function handily and safely exposes the $ shortcut as jQuery by making it a local parameter to the anonymous function. Since parameters will override any globals only for the scope of a function this will not affect any other user/library code outside of it.

Finally, where the anonymous function is executed jQuery is passed in as the first paramter to fill $.

So when boiled down, this is just a shortcut taken by plugin developers so that they can safely and reliably use $; if you don’t mind using jQuery everywhere instead then this is totally optional.