Javascript - Why calling function defined inside a closour?

Question

I have seen many js frameworks (including jquery) using closure around their main function scope. For example,

var obj = (function(){
    return {
        test : function(){
            alert('test');
        }
    }
})();
obj.test()

Whats the need that extra 'closure' around the 'function'? Or whats the difference if we are using it like,

var obj = function(){
    return {
        test : function(){
            alert('test');
        }
    }
}();
obj.test()

Both have the same behavior and function definition itself puts all the local variable inside a new scope... so why the extra closure?

http://stackoverflow.com/questions/6645766/why-are-parenthesis-used-to-wrap-a-javascript-function-call — Stanley Stuart, May 10 '12 at 09:04

gdoron · Accepted Answer · 2012-05-10T09:02:46.913

4

It adds the "big"object\library functions, and not adding them to the global object.

The two options you pasted are just like the difference between:

var foo = (2);
var foo = 2;

No difference...

Update:

Now I undersatnd your question, parentheses don't create new scope in javascript, only functions.

edited May 10 '12 at 09:02

answered May 10 '12 at 08:51

gdoron

@gdoron I thought he is asking why not just `var obj = { test : function(){ alert('test'); } };` – xdazz May 10 '12 at 09:06

score 0 · Answer 2 · answered May 10 '12 at 09:10

0

That is just a convention to be able to easily distinguish self-executing functions from normal functions.

answered May 10 '12 at 09:10

stewe

2 Answers2