scroll-parent.js

const regex = /(auto|scroll)/;

const parents = function (node, ps) {
	if (node.parentNode === null) { return ps; }

	return parents(node.parentNode, ps.concat([node]));
};

const style = function (node, prop) {
	return getComputedStyle(node, null).getPropertyValue(prop);
};

const overflow = function (node) {
	return style(node, "overflow") + style(node, "overflow-y") + style(node, "overflow-x");
};

const scroll = function (node) {
	return regex.test(overflow(node));
};

const scrollParent = function (node) {
	if (!(node instanceof HTMLElement || node instanceof SVGElement)) {
		return;
	}

	const ps = parents(node.parentNode, []);

	for (let i = 0; i < ps.length; i += 1) {
		if (scroll(ps[i])) {
			return ps[i];
		}
	}

	return document.body;
};

export default scrollParent;