Question

Is there a reason that this would not work?

 var xcurrent = parseInt(window.document.getElementById('firstdiv').style.left);
 var ycurrent = parseInt(window.document.getElementById('firstdiv').style.top);

I’m being told it’s not an integer NaN.

Answer 1

Is there a reason that this would not work?

var xcurrent = parseInt(window.document.getElementById(‘firstdiv’).style.left);

Quite a few, but the likely ones are:

1. If element with id ‘firstdiv’ doesn’t exist, window.document.getElementById('firstdiv') will return null. Attempting to access the style property of null will throw an error. That’s not the result you specified though.

2. The value returned by .style.left is an empty string. In that case, parseInt returns NaN per ECMA-262.

A safer approach is:

var el = document.getElementById('firstdiv');
var xcurrent

if (el) {
  xcurrent = parseInt(el.style.left);

  if (isNaN(xcurrent)) { 
    // there was no value for xcurrent, what now?

As Nathan said, you can use offsetLeft instead.