What is this? (function(){ })() [duplicate]

Question

Possible Duplicates:
What does this JavaScript snippet mean?
Location of parenthesis for auto-executing anonymous JavaScript functions?

(function(){

    //something here...

})() <--//This part right here.

What exactly is this )()?
What if I change it to this ())?

(function(){

    //something here...

}()) <--//Like this

Answer 1

This declares an anonymous function and calls it immediately.

The upside of doing this is that the variables the function uses internally are not added to the current scope, and you are also not adding a function name to the current scope either.

It is important to note that the parentheses surrounding the function declaration are not arbitrary. If you remove these, you will get an error.

Finally, you can actually pass arguments to the anonymous function using the extra parentheses, as in

(function (arg) {
   //do something with arg
})(1);

See http://jsfiddle.net/eb4d4/