What is benefit of using (function(){…})() in JavaScript

Question

I noticed in JQuery that the following code structure is used

(function(){var l=this,g,y=l.jQuery,p=l.$,...})()

Which seems to create a function, and call it.

What is the benefit of taking this approach versus having the contents of the function inline?

Answer 1

It creates a closure to prevent conflicts with other parts of code. See this:

• http://docs.jquery.com/Plugins/Authoring

Particularly handy if you have some other library that uses the $() method and you have to retain the ability to use that with jQuery also. Then you can create a closure such as this:

(function($) {
    // $() is available here
})(jQuery);

Answer 2

It creates a scope for variables, in particular defining $ for example to bind to jQuery, no matter what other libraries overwrite it. Think of it as an anonymous namespace.

Answer 3

With self invoking anonymous function you create a local scope, it's very efficient and it directly calls itself.

You can read about it here

Answer 4

It's just like:

var foo = function(){var l=this,g,y=l.jQuery,p=l.$,...};
foo();

But more simple and do not need a global variable.

Answer 5

It allows to have local variables and operations inside of the function, instead of having to transform them to global ones.