JAVASCRIPT:Hashtable in Javascript

function Hashtable(){

   this.hashtable = new Object();

}

/* privileged functions */

Hashtable.prototype.clear = function(){

   this.hashtable = new Object();

}             

Hashtable.prototype.containsKey = function(key){

   var exists = false;

   for (var i in this.hashtable) {

       if (i == key && this.hashtable[i] != null) {

           exists = true;

           break;

       }   

   }

   return exists;

}

Hashtable.prototype.containsValue = function(value){

   var contains = false;

   if (value != null) {

       for (var i in this.hashtable) {

           if (this.hashtable[i] == value) {

               contains = true;

               break;

           }

       }

   }       

   return contains;

}

Hashtable.prototype.get = function(key){

   return this.hashtable[key];

}

Hashtable.prototype.isEmpty = function(){

   return (parseInt(this.size()) == 0) ? true : false;

}

Hashtable.prototype.keys = function(){

   var keys = new Array();

   for (var i in this.hashtable) {

       if (this.hashtable[i] != null)

           keys.push(i);

   }

   return keys;

}

Hashtable.prototype.put = function(key, value){

   if (key == null || value == null) {

       throw "NullPointerException {" + key + "},{" + value + "}";

   }else{

       this.hashtable[key] = value;

   }

}

Hashtable.prototype.remove = function(key){

   var rtn = this.hashtable[key];

   this.hashtable[key] = null;

   return rtn;

}   

Hashtable.prototype.size = function(){

   var size = 0;

   for (var i in this.hashtable) {

       if (this.hashtable[i] != null)

           size ++;

   }

   return size;

}

Hashtable.prototype.toString = function(){

   var result = "";

   for (var i in this.hashtable)

   {   

       if (this.hashtable[i] != null)

           result += "{" + i + "},{" + this.hashtable[i] + "}\n"; 

   }

   return result;

}                                 

Hashtable.prototype.values = function(){

   var values = new Array();

   for (var i in this.hashtable) {

       if (this.hashtable[i] != null)

           values.push(this.hashtable[i]);

   }

   return values;

}                                 

Hashtable.prototype.entrySet = function(){

   return this.hashtable;

}