findAncestor.js

/**
 * Return the first ancestor for which the {@code predicate} returns true.
 * @param {Node} node The node to check.
 * @param {function(Node):boolean} predicate The function that tests the
 *     nodes.
 * @return {Node} The found ancestor or null if not found.
 */
function findAncestor(node, predicate) {
	var last = false;
	while (node != null && !(last = predicate(node))) {
		node = node.parentNode;
	}
	return last ? node : null;
}