(function () {
	if (typeof window.Element === 'undefined' || 'classList' in document.documentElement) return;

	var prototype = Array.prototype,
		push = prototype.push,
		splice = prototype.splice,
		join = prototype.join;

	function DOMTokenList(el) {
		this.el = el;
		// The className needs to be trimmed and split on whitespace
		// to retrieve a list of classes.
		var classes = el.className.replace(/^\s+|\s+$/g,'').split(/\s+/);
		for (var i = 0; i < classes.length; i++) {
			push.call(this, classes[i]);
		}
	}

	DOMTokenList.prototype = {
		add: function(token) {
			if(this.contains(token)) return;
			push.call(this, token);
			this.el.className = this.toString();
		},
		contains: function(token) {
			return this.el.className.indexOf(token) != -1;
		},
		item: function(index) {
			return this[index] || null;
		},
		remove: function(token) {
			if (!this.contains(token)) return;
			for (var i = 0; i < this.length; i++) {
				if (this[i] == token) break;
			}
			splice.call(this, i, 1);
			this.el.className = this.toString();
		},
		toString: function() {
			return join.call(this, ' ');
		},
		toggle: function(token) {
			if (!this.contains(token)) {
				this.add(token);
			} else {
				this.remove(token);
			}

			return this.contains(token);
		}
	};

	window.DOMTokenList = DOMTokenList;

	function defineElementGetter (obj, prop, getter) {
		if (Object.defineProperty) {
			Object.defineProperty(obj, prop,{
				get : getter
			});
		} else {
			obj.__defineGetter__(prop, getter);
		}
	}

	defineElementGetter(Element.prototype, 'classList', function () {
		return new DOMTokenList(this);
	});
})();