What is the purpose of a self executing function in javascript?

Question

In javascript, when would you want to use this:

(function(){
    //Bunch of code...
})();

over this:

//Bunch of code...
         


        

Answer 1

Is there a parameter and the "Bunch of code" returns a function?

var a = function(x) { return function() { document.write(x); } }(something);

Closure. The value of something gets used by the function assigned to a. something could have some varying value (for loop) and every time a has a new function.