Hi, check this out:
var y = function(){

return "asdfg";


var z = function(){

      var x = new y();
      var div = document.createElement('div');
      div.innerHTML = x;
            code goes on with hundreds of other functions and stuff,
            the entire application is build using only js, all the data comes trough sockets and the elements are created using js.
as you see, inside 'z' there is 'x' and 'div', now suppose those two guys are only used there, no where else, so, in that case, do they still 'alive' inside the js on the web browser? do they vanish? do i need to set them to null to avoid any extra memory from being used on useless stuff?

btw, this might be something idiot, but i wrote like 20k lines using js and all the elements are created using js, the applications stays up for like 8 hours until they close and it starts all over again on the other day. but for 8 hours, as it is a little big, i`m afraid i will get slow.

thank you,
sorry for the bad English,