JavaScript Hashtable based on MS AJAX

I was looking to implement a JavaScript hashtable and after find a number of near identical implementations, I decicded to modify one that I found at http://alexrazon.blogspot.com/2006/11/javascript-hashtable-implementation.html to be based on the MS Ajax Patern.

Anyways, here it is:

Mbccs.Psp.Web.Manager.Hashtable = function() {
 this._hash = new Array();
 this._keys = new Array();
 this._getEnum = new Array();
 this._count = 0;
}

Mbccs.Psp.Web.Manager.Hashtable.prototype = {
 getAt : function(index) {
  return this._hash[this._getEnum[index]];
 },
 
 get : function (key) {
  return this._hash[key];
 },

 remove : function (key) {
  for (var i = this._keys.length - 1; i >= 0; i--) {
   if (this._keys[i] == key) {
    this._keys.splice(i, 1);
    this._getEnum.splice(i, 1);
    this._hash[key] = null;

    this._count = this._keys.length;
   }
  }
 },

 put : function (key, value) {
  if (value == null)
   return null;
  if (this._hash[key] == null) {
   this._keys[this._keys.length] = key;
   this._count = this._keys.length;
   this._getEnum[this._count - 1] = key;
  }

  this._hash[key] = value;
 }
}

Mbccs.Psp.Web.Manager.Hashtable.registerClass('Mbccs.Psp.Web.Manager.Hashtable');

if(typeof(Sys) !== 'undefined')
 Sys.Application.notifyScriptLoaded();