Gets all elements below the specified point. Checks to see if browser already has method before using a manual method. Originally found https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/dTYbg4_S2b8/bEtoAnkP0swJ

elementsFromPoint.js

// returns a list of all elements under the cursor
// 
function elementsFromPoint(x,y) {
	var elements = [], previousPointerEvents = [], current, i, d;

	if(typeof document.elementsFromPoint === "function")
		return document.elementsFromPoint(x,y);
	if(typeof document.msElementsFromPoint === "function")
		return document.msElementsFromPoint(x,y);
	
    // get all elements via elementFromPoint, and remove them from hit-testing in order
	while ((current = document.elementFromPoint(x,y)) && elements.indexOf(current)===-1 && current != null) {
          
        // push the element and its current style
		elements.push(current);
		previousPointerEvents.push({
            value: current.style.getPropertyValue('pointer-events'),
            priority: current.style.getPropertyPriority('pointer-events')
        });
          
        // add "pointer-events: none", to get to the underlying element
		current.style.setProperty('pointer-events', 'none', 'important'); 
	}

    // restore the previous pointer-events values
	for(i = previousPointerEvents.length; d=previousPointerEvents[--i]; ) {
		elements[i].style.setProperty('pointer-events', d.value?d.value:'', d.priority); 
	}
      
    // return our results
	return elements;
}