js offset element func

/**
* relates an element's border box to the document origin
*
* @param {DOMObject} current element
* @return {Object} top and left cooridanets of element relative to origin document
*/
function offset(element) {

	const rect = element.getBoundingClientRect();
	const win = element.ownerDocument.defaultView;

	return {
		top: rect.top + win.pageYOffset,
		left: rect.left + win.pageXOffset;
	}
}