What's the difference between:

function bar()

{

  for (x=0; x< 100; x++) {}

}

And

function bar()

{

  var x;

  for (x=0; x< 100; x++) {}

}

If x wasn't declared outside of that function, and so it wasn't a global variable? I always wonder this because I generally don't declare throwaway variables which are used only in a loop, but I wonder if this might break comparability in a browser or such.