[ruslan_mart]

Предлагаю своё расширение:

Element.prototype.getChilds: function(selector) {
	var originID = this.id;
	this.id = '___' + Date.now();
	var elements = document.querySelectorAll('#' + this.id + ' > ' + (selector || '*'));
	this.id = originID;
	return elements;
};

element.getChilds('div');

element.getChilds('.foo');

element.getChilds('[foo="bar"]');