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

This are anonymous function which is executed in place.The best usage of this is to set some context or environment settings or have some side effect on load.

This are heavily used by Ajax Toolkits like JQuery,Dojo,etc to performs load time magic and workaround many browser quirks and shortcomings.