JonathanNeal.js

var _nodeUnique = function (nodeArray) {
	var a = -1, len = nodeArray.length, b = -1, ret = new Array();

	while (++a < len) {
    while (++b < len && nodeArray[b] === nodeArray[a])
			;
    
    ret[b] = nodeArray[a];  
	}

	return ret;
};

var _nodeSortFn = (document.documentElement.sourceIndex != null) ?
function (a, b) {
  return a.sourceIndex - b.sourceIndex;
} :
function (a, b) {
  return 3 - (a.compareDocumentPosition(b) & 6);
};

var _nodeSort = function (nodeArray) {
	return _nodeUnique(nodeArray.sort(_nodeSortFn));
};

/* add */
Y.Node.prototype.add = function (elem, context) {
    return Y.all(this).add(elem, context);
};
Y.NodeList.prototype.add = function (elem, context) {
	var collection = this._nodes;

	if (context && Y.Lang.isString(elem)) {
		((context._nodes) ? context : Y.Node.all(context)).each(function (node) {
			collection = collection.concat(node.all(elem)._nodes);
		});
	}
	else if (elem) {
		collection = collection.concat(elem._nodes || Y.Node.all(elem)._nodes);
	}

	return Y.Node.all(_nodeSort(collection));
};

/* children */
Y.Node.prototype.children = function (selector) {
	return this.get('children').filter(selector);
};
Y.NodeList.prototype.children = function (selector) {
	var collections = new Array();
  var nodes = this._nodes, i = -1, node, j = -1;

  while((node = nodes[++i]))
	{	
    collections[++j] = node.children().filter(selector)._nodes;
	}

	return Y.Node.all(Array.prototype.concat.apply(new Array(), collections));
};

/* parent */
Y.Node.prototype.parent = function (selector) {
	return this.get('parentNode').filter(selector);
};
Y.NodeList.prototype.parent = function (selector) {
	var collection = new Array();
  var nodes = this._nodes, i = -1, node, j = -1;
  var parent;
  
  while((node = nodes[++i]))
  {
		if (parent = node.parent(selector)) {
			collection[++j] = node.parent(selector)._node;
		}
	}
  
	return Y.Node.all(_nodeSort(collection));
};

/* empty */
Y.Node.prototype.empty = function () {
	this.get('children').remove(true);
	this.get('childNodes').remove();

	return this;
};
Y.NodeList.importMethod(Y.Node.prototype, ['empty']);

/* eq */
Y.NodeList.prototype.eq = function (index) {
	return this.item((index < 0) ? this.size() + index : index);
};

/* filter */
Y.NodeList.prototype.filterByString = Y.NodeList.prototype.filter;
Y.Node.prototype.filter = function (selector) {
    return Y.all(this).filter(selector).item(0);
};
Y.NodeList.prototype.filter = function (selector) {
	var collection = new Array();

	if (Y.Lang.isString(selector)) {
		return this.filterByString(selector);
	}
	else if (typeof selector == 'function') {
		var nodes = this._nodes, i = -1, node, j = -1;
    
    while((node = nodes[++i]))
    {
			if (selector(i) !== false) {
				collection[++j] = node;
    }

		return Y.Node.all(collection);
	}
	else {
		return this;
	}
};

/* find */
Y.NodeList.prototype.find = function (selector) {
	var collections = new Array();
  var nodes = this._nodes, i = -1, node, j = -1;

  while((node = nodes[++i]))
		collections[++j] = node.all(selector)._nodes;

	return Y.Node.all(_nodeSort(Array.prototype.concat.apply(new Array(), collections)));
};

/* get */
Y.NodeList.prototype.get = function (index) {
	return (!Y.Lang.isUndefined(index)) ? this._nodes[index] : this._nodes;
};

/* is */
Y.Node.prototype.is = Y.Node.prototype.test;
Y.NodeList.prototype.is = function (selector) {
	var boolean = true;
  var nodes = this._nodes, i = -1, node;

  while((node = nodes[++i]) && node.is(selector))
		;

	return node == null;
};