Question

every time when I see a jQuery plugin like this:

(function($) {
    $.fn.example = function(options) {
        return this.each(function() {
           return 'Example!';
        });
    }

})(jQuery);

I am wondering about the wrapping function:

(function($) {
   // ...
})(jQuery);

Is it necessary? If yes, why? And if not, what are the alternatives/advantages?

Answer 1

It’s done this way to ensure the plugin is in its own scope and doesn’t interfere with anything.

A lot of libraries use $ as their shortcut, so we’re passing jQuery and assigning it as $ to make sure it doesn’t interfere.

jQuery explains its use in their docs: http://docs.jquery.com/Plugins/Authoring