(function () {

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

// adds indexOf to Array prototype for IE support
if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(obj, start) {
        for (var i = (start || 0), j = this.length; i < j; i++) {
            if (this[i] === obj) { return i; }
        }
        return -1;
    }
}

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

function DOMTokenList(el) {  
  this._element = el;
  if (el.className != this._classCache) {
    this._classCache = el.className;

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

function setToClassName(el, classes) {
  el.className = classes.join(' ');
}

DOMTokenList.prototype = {
  add: function(token) {
    if(this.contains(token)) return;
    push.call(this, token);
    setToClassName(this._element, slice.call(this, 0));
  },
  contains: function(token) {
    return indexOf.call(this, token) !== -1;
  },
  item: function(index) {
    return this[index] || null;
  },
  remove: function(token) {
    var i = indexOf.call(this, token);
     if (i === -1) {
       return;
     }
    splice.call(this, i, 1);
    setToClassName(this._element, slice.call(this, 0));
  },
  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);            
});

})();