哈希表(hashtable)的javascript简单实现

javascript中没有像c#,java那样的哈希表(hashtable)的实现。在js中,object属性的实现就是hash表,因此只要在object上封装点方法,简单的使用obejct管理属性的方法就可以实现简单高效的hashtable。

首先简单的介绍关于属性的一些方法：

属性的枚举:

for/in循环是遍历对象属性的方法。如

 var obj = {name : 'obj1',age : 20,height : '176cm'
}var str = '';
for(var name in obj)
{str += name + ':' + obj[name] + '\n';
}
alert(str);

输出为：name:obj1

　　age:20

　　height:176cm

检查属性是否存在:

in运算符可以用来测试一个属性是否存在。

this.containsKey = function ( key )
{return (key in entry);
}

删除属性

使用delete运算符来删除一个对象的属性。使用delete删除的属性，for/in将不会枚举该属性，并且in运算符也不会检测到该属性。

 delete entry[key];delete obj.name;

下面是哈希表(hashtable)的js的实现方法：

function HashTable()
{var size = 0;var entry = new Object();this.add = function (key , value){if(!this.containsKey(key)){size ++ ;}entry[key] = value;}this.getValue = function (key){return this.containsKey(key) ? entry[key] : null;}this.remove = function ( key ){if( this.containsKey(key) && ( delete entry[key] ) ){size --;}}this.containsKey = function ( key ){return (key in entry);}this.containsValue = function ( value ){for(var prop in entry){if(entry[prop] == value){return true;}}return false;}this.getValues = function (){var values = new Array();for(var prop in entry){values.push(entry[prop]);}return values;}this.getKeys = function (){var keys = new Array();for(var prop in entry){keys.push(prop);}return keys;}this.getSize = function (){return size;}this.clear = function (){size = 0;entry = new Object();}
}

测试：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml">
<head><title>HashTable</title><script type="text/javascript" src="/js/jquery.js"></script><script type="text/javascript" src="/js/HashTable.js"></script><script type="text/javascript">function MyObject(name){this.name = name;this.toString = function(){return this.name;}}$(function(){var map = new HashTable();map.add("A","1");map.add("B","2");map.add("A","5");map.add("C","3");map.add("A","4");var arrayKey = new Array("1","2","3","4");var arrayValue = new Array("A","B","C","D");map.add(arrayKey,arrayValue);var value = map.getValue(arrayKey);var object1 = new MyObject("小4");var object2 = new MyObject("小5");map.add(object1,"小4");map.add(object2,"小5");$('#console').html(map.getKeys().join('|') + '<br>');})</script>
</head>
<body><div id="console"></div>
</body>
</html>