[jQuery] offSetTop & offsetLeft return NULL

[jQuery] offSetTop & offsetLeft return NULL


I have these functions:
var e_w = jQuery("a").eq(index).width();
var e_h = jQuery("a").eq(index).height();
var e_ox = jQuery("a").eq(index).offsetLeft;
var e_oy = jQuery("a").eq(index).offsetTop;
the first 2 return numbers such as 50 and 100. But the last 2 each
return NULL.
Why are they returning NULL? How can I get the offset of an element
given it's index in terms of "a" tags?