Possible Duplicate:
Are “(function ( ) { } ) ( )” and “(function ( ) { } ( ) )” functionally equal in JavaScript?
This is something I haven’t quite figured out yet, but I have been using function(){}() just because my VIM syntax highlight screws up if I add the parenthesis, although I’ve seen (function(){})() around many times, maybe its an IE thing?
edit:
var singleton = function() { // code }(); var singleton = (function() { // code })();
Peter Michaux discusses the difference in An Important Pair of Parens.
Basically the parentheses are a convention to denote that an immediately invoked function expression is following, not a plain function. Especially if the function body is lengthy, this reduces surprises,