offsetTop only looks at the element's parent. Just loop through parent nodes until you run out of parents and add up their offsets.
function getPosition(element) {
var xPosition = 0;
var yPosition = 0;
while(element) {
xPosition += (element.offsetLeft - element.scrollLeft + element.clientLeft);
yPosition += (element.offsetTop - element.scrollTop + element.clientTop);
element = element.offsetParent;
}
return { x: xPosition, y: yPosition };
}
UPDATE: This answer has some problems, values will have tiny differences compare to what it should be and will not work correctly in some cases.
Check @eeglbalazs's answer, which is accurate.
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