A function that takes an element and finds the parent element that scrolls. Useful in very specific circumstances

getScrollingParent.js

/**
 * Takes an element and finds the parent element that would scroll.
 *
 * @param  {Element} element
 *         Element whose scrolling parent should be returned.
 * @return {Element|null}
 *         Parent element that scrolls. If no parent can be found, null is
 *         returned.
 */
function getScrollingParent(element) {

	const parent = element?.parentElement;

	switch (
		parent &&
		parent.nodeType === Node.ELEMENT_NODE &&
		window.getComputedStyle(parent, null).getPropertyValue('overflow-y')
	) {

	case 'visible':
		return getScrollingParent(parent);

	case 'auto':
	case 'scroll':
		return parent;

	default:
		return null;

	}

}