function Hashtable()
{
    this._hash = new Object();
    this.add = function(key,value)
    {
        if(typeof(key)!="undefined")
        {
           this._hash[key]=typeof(value)=="undefined"?null:value;
                return true;
        }
        else {
            return false;
        }
    }
    this.remove        = function(key){delete this._hash[key];}
    this.count        = function(){var i=0;for(var k in this._hash){i++;} return i;}
    this.items        = function(key){return this._hash[key];}
    this.contains    = function(key){ return typeof(this._hash[key])!="undefined";}
    this.clear        = function(){for(var k in this._hash){delete this._hash[k];}}
}

