一个用javascript写的hashtable类

<script language="javascript" type="text/javascript">

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";} //判断key是否存在
    this.clear        = function(){for(var k in this._hash){delete this._hash[k];}}
 this.hasvalue        = function(value){
  for(var k in this._hash){
   if(this._hash[k]==value){
    return true;
   }
  }
  return false;
 }
 this.getallvalues        = function(){
  var tmp="";
  for(var k in this._hash){
   tmp += k+","+a._hash[k]+";";
  }
  return tmp;
 }
 this.getjosnvalues        = function(){
  var tmp="{";
  for(var k in this._hash){
   tmp += k+":"+a._hash[k]+",";
  }
  tmp+="}";
  return tmp;
 }
 this.getjosnitems        = function(){
  var tmp="[";
  for(var k in this._hash){
   tmp += "{"+k+":"+a._hash[k]+"},";
  }
  tmp=tmp.substring(0,tmp.length-1)+"]";
  return tmp;
 }
}

var a = new Hashtable();

a.add("aa");
a.add("bb",2342);
a.add("bb",2344);

alert(a.hasvalue(2342));

a.add("cc",2342);

for(var k in a._hash){
 alert(k+":"+a._hash[k]);
}

alert("移除");
a.remove("aa");

for(var k in a._hash){
 alert(k+":"+a._hash[k]);
}

alert("a.getallvalues():"+a.getallvalues());
alert("this.getjosnitems():"+this.getjosnitems());

/*
alert("计算总数");
alert(a.count());
alert("显示bb是否是数字");
alert(a.contains("bb"));
alert("显示aa是否是数字");
alert(a.contains("aa"));
alert("显示bb内容");
alert(a.items("bb"));
alert("显示aa内容");
alert(a.items("aa"));
*/
</script>