JS自定义对象实现Java中Map对象功能的方法

/** 
 * @version 1.0 
 * 用于实现页面 Map 对象，Key只能是String，对象随意 
 */  
var Map = function(){  
    this._entrys = new Array();  
      
    this.put = function(key, value){  
        if (key == null || key == undefined) {  
            return;  
        }  
        var index = this._getIndex(key);  
        if (index == -1) {  
            var entry = new Object();  
            entry.key = key;  
            entry.value = value;  
            this._entrys[this._entrys.length] = entry;  
        }else{  
            this._entrys[index].value = value;  
        }          
    };  
    this.get = function(key){  
        var index = this._getIndex(key);  
        return (index != -1) ? this._entrys[index].value : null;  
    };  
    this.remove = function(key){  
        var index = this._getIndex(key);  
        if (index != -1) {  
            this._entrys.splice(index, 1);  
        }  
    };  
    this.clear = function(){  
        this._entrys.length = 0;;  
    };  
    this.contains = function(key){  
        var index = this._getIndex(key);  
        return (index != -1) ? true : false;  
    };  
    this.getCount = function(){  
        return this._entrys.length;  
    };  
    this.getEntrys =  function(){  
        return this._entrys;  
    };  
   this._getIndex = function(key){  
        if (key == null || key == undefined) {  
            return -1;  
        }  
        var _length = this._entrys.length;  
        for (var i = 0; i < _length; i++) {  
            var entry = this._entrys[i];  
            if (entry == null || entry == undefined) {  
                continue;  
            }  
            if (entry.key === key) {//equal  
                return i;  
            }  
        }  
        return -1;  
    };  
}

// 自定义Map对象  
var map = new Map();  
map.put("a","a");  
alert(map.get("a"));  
map.put("a","b");  
alert(map.get("a"));