A Javascript function

Please explain the following way of writing a function in javascript functions :

(function (){
 // some code 
})()

I understand the fact that because of the trailing braces " () ", the function will execute immediately but but what does enclosing the function in the braces mean?

Solution

Your syntax is incorrect. Edit: fixed.

Look at a normal function definition that you want to call once and only once:

function add(x,y) {
   var z = x + y; 
   // do something with z
}

add(2,3);

You could reduce this code so that you execute it straight away, there is no need to name it add:

(function(x ,y) {
   var z = x + y; 
   // do something with z
})(2,3)

Note how we have surrounded the function with a set of parenthesis to make it a callable expression. This pattern is often used to create a closure (capture the state of) certain variables, for example:

jQuery.noConflict(); //Disables the use of $ in the global scope
(function($) {

   //Safely use $ inside this function
   $('.link').click(function(e) {
      //etc
   });

})(jQuery);