Strange JavaScript syntax like this: (function(){//code}) ();?

Question

What does the below JavaScript mean? Why is the function embedded inside ()?

(function() {
    var b = 3;
    a += b;
}) ();

Answer 1

It's functionaly equivalent to doing something like:

var myFunc = function(){
    var b = 3;
    a += b;
};

myFunc();

It's got the parenthesis around it (and trailing) so that the function is called immediately. As others have said, the concept is called an anonymous function.