function Hashtable() 
{ 
 this._hash = new Object(); 
 this.add = function(key,value){ 
 if(typeof(key)!="undefined"){ 
 if(this.contains(key)==false){ 
 this._hash[key]=typeof(value)=="undefined"?null:value; 
 return true; 
 } else { 
 return false; 
 } 
 } 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];}} 
} 
var a = new Hashtable(); 
a.add("aa"); 
a.add("bb",2342); 
a.add("bb",2342); 
a.remove("aa"); 
alert(a.count()); 
alert(a.contains("bb")); 
alert(a.contains("aa")); 
alert(a.items("bb")); 
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