classList(DOMTokenList) polyfills

classList

;(function() {
	if ( !Element.__defineGetter__ || Element.prototype.hasOwnProperty("classList") ) return;

	function classList(elm) {
		this.elm = elm;
	}

	classList.prototype = {
		add: function(klass) {
			var _elm = this.elm,
				_thisClass = _elm.className;
			if ( _elm.classList.contains(klass) ) return false;
			if ( !_thisClass || _thisClass.length === 0 ) {
				_elm.className = klass;
			} else {
				_elm.className += " " + klass;
			}
		},
		remove: function(klass) {
			var _elm = this.elm,
				_thisClass = _elm.className,
				_thisClassSplit = _thisClass.split(" "),
				i;
			if ( !_elm.classList.contains(klass) ) return;
			if ( _thisClass === klass ) {
				_elm.className = "";
				return;
			}
			for ( i = 0; i < _thisClassSplit.length; i++ ) {
				if ( _thisClassSplit[i] !== klass ) continue;
				delete _thisClassSplit[i];
				break;
			}
			_elm.className = _thisClassSplit.join(" ");
		},
		toggle: function(klass) {
			var _elm = this.elm;
			if ( _elm.classList.contains(klass) ) {
				_elm.classList.remove(klass);
			} else {
				_elm.classList.add(klass);
			}
		},
		contains: function(klass) {
			return this.elm.className.indexOf(klass) !== -1;
		}
	}

	Element.prototype.__defineGetter__("classList", function() {
		return new classList(this);
	});
}());