find-overflow-elements.js

// originaly based on code from https://css-tricks.com/findingfixing-unintended-body-overflow/
// improved to handle absolute positioned elements shifted to right making overflow happend.
function findOverflow(){
	var docWidth = document.documentElement.offsetWidth;

	[].forEach.call(
			document.querySelectorAll('*'),
			function(el) {
				var rect= el.getBoundingClientRect();
				if (el.offsetWidth > docWidth ||rect.right>docWidth) {
					console.log(el);
				}
			}
	);
}
findOverflow(); // call it as script loads. Also you can call it later manually from a console.