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';}this.clear = function(){for(var k in this._hash){delete this._hash[k];}}}var a = new Hashtable();a.add('aa');a.add('bb','你好哦');a.add('cc','hello');//a.remove('aa');alert(a.count());alert(a.contains('bb'));//alert(a.contains('cc'));alert(a.items('bb'));</script>