[WIP] Pure JavaScript implementation of "Document Object Model Traversal".

traversal.js

(function(window, document) {
if ( !window.NodeFilter ) {

	var NodeFilter = function() {};

	NodeFilter.FILTER_ACCEPT = 1;
	NodeFilter.FILTER_REJECT = 2;
	NodeFilter.FILTER_SKIP   = 3;

	NodeFilter.SHOW_ALL                    = 0xFFFFFFFF;
	NodeFilter.SHOW_ELEMENT                = 0x00000001;
	NodeFilter.SHOW_ATTRIBUTE              = 0x00000002;
	NodeFilter.SHOW_TEXT                   = 0x00000004;
	NodeFilter.SHOW_CDATA_SECTION          = 0x00000008;
	NodeFilter.SHOW_ENTITY_REFERENCE       = 0x00000010;
	NodeFilter.SHOW_ENTITY                 = 0x00000020;
	NodeFilter.SHOW_PROCESSING_INSTRUCTION = 0x00000040;
	NodeFilter.SHOW_COMMENT                = 0x00000080;
	NodeFilter.SHOW_DOCUMENT               = 0x00000100;
	NodeFilter.SHOW_DOCUMENT_TYPE          = 0x00000200;
	NodeFilter.SHOW_DOCUMENT_FRAGMENT      = 0x00000400;
	NodeFilter.SHOW_NOTATION               = 0x00000800;

	NodeFilter.prototype.acceptNode = function(n) {
		return NodeFilter.FILTER_ACCEPT;
	};

	window.NodeFilter = NodeFilter;
}

if ( !document.createTreeWalker ) {

	/*
	 * http://codesearch.google.com/#OAMlx_jo-ck/src/third_party/WebKit/Source/WebCore/dom/TreeWalker.cpp
	 * http://www.w3.org/TR/DOM-Level-2-Traversal-Range/traversal.html
	 */

	function TreeWalker(root, whatToShow, filter, entityReferenceExpansion) {
		// RADAR
		// This is imho not necessary 'cause IE<9 doesn't support overwriting
		// property setters on non-DOM objects and other browsers have already
		// TreeWalker support.
		// Maybe TreeWalker can be implemented as DOM object?
		// Note: For IE we use Object.defineProperty!
		var currentNode;
		this.__defineSetter__('currentNode', function(node) {
			if ( node === null ) { throw( DOMException.NOT_SUPPORTED_ERR ); }
			return currentNode = node;
		});
		this.__defineGetter__('currentNode', function() {
			return currentNode;
		});

		this.parentNode = function() {
			var node, filterResult = NodeFilter.FILTER_ACCEPT;

			while ( node !== root ) {
				node = this.currentNode.parentNode;
				if ( !node ) { return null; }

				if ( typeof(filter) == 'function' ) try {
					filterResult = filter.acceptNode( node );
				} catch (e) {
					return null;
				}

				if ( filterResult === NodeFilter.FILTER_ACCEPT ) {
					return currentNode = node;
				}
			}
			return null;
		};
		this.firstChild = function() {
			for (var node = node.firstChild, filterResult = NodeFilter.FILTER_ACCEPT; node;) {

				if ( typeof(filter) == 'function' ) try {
					filterResult = filter.acceptNode( node );
				} catch (e) {
					return null;
				}

				switch ( filterResult ) {
					case NodeFilter.FILTER_ACCEPT: return currentNode = node;
					case NodeFilter.FILTER_SKIP:
						if ( node.firstChild ) {
							node = node.firstChild;
							continue;
						}

						break;
					case NodeFilter.FILTER_REJECT: break;
				}

				do {
					if ( node.nextSibling ) {
						node = node.nextSibling;
						break;
					}

					node = node.parentNode;
					if ( node === root || node === currentNode ) {
						return null;
					}
				} while ( node )
			}

			return null;
		};

		this.lastChild = function() {};
	};

	(function(fn) {
		fn.previousSibling = function() {};
		fn.nextSibling = function() {};
		fn.previousNode = function() {
			var node;

			node = this.previousSibling();
			if ( node ) { return this.lastChild() || node; }
			node = this.parentNode();
			if ( node ) { return this.previousNode(); }

			return node;
		};
		fn.nextNode = function() {
			var node;

			node = this.firstChild() || this.nextSibling();
			if ( node ) { return node; }
			node = this.parentNode();
			if ( node ) { return this.nextNode(); }

			return node;
		};
	})(TreeWalker.prototype)

	document.createTreeWalker = TreeWalker;
}
})(window, document);