@lagrange/animator/src/functions/getContextScrollTop.js

This library helps making parallax animations on scroll. It is built with performance in mind, as it doesn't need to relayout or paint to operate.

/**
 * @param {Element} context 
 * @param {Scrollbar} scrollbar 
 */
export default function getContextScrollTop(context) {
	let ctx = context;
	if (context.tagName === 'HTML') ctx = document.scrollingElement || context;

	return ctx.scrollTop;
}