JavaScript自定义Map函数（IE8及以上兼容）

/** 
 *  
 * 描述：js实现的map方法 
 * @returns {Map} 
 */  

function Map() {
    var struct = function(key, value) {
        this.key = key;
        this.value = value;
    };
    // 添加map键值对  
    var put = function(key, value) {
        for (var i = 0; i < this.arr.length; i++) {
            if (this.arr[i].key === key) {
                this.arr[i].value = value;
                return;
            }
        }
        ;
        this.arr[this.arr.length] = new struct(key, value);
    };
    //  根据key获取value   
    var get = function(key) {
        for (var i = 0; i < this.arr.length; i++) {
            if (this.arr[i].key === key) {
                return this.arr[i].value;
            }
        }
        return null;
    };
    //   根据key删除  
    var remove = function(key) {
        var v;
        for (var i = 0; i < this.arr.length; i++) {
            v = this.arr.pop();
            if (v.key === key) {
                continue;
            }
            this.arr.unshift(v);
        }
    };
    //   获取map键值对个数  
    var size = function() {
        return this.arr.length;
    };
    // 判断map是否为空    
    var isEmpty = function() {
        return this.arr.length <= 0;
    };

    var forEach = function(callback) {
        for (var i = 0; i < this.arr.length; i++) {
            callback(this.arr[i].value, this.arr[i].key);
        }
    }
    this.arr = new Array();
    this.get = get;
    this.put = put;
    this.remove = remove;
    this.size = size;
    this.isEmpty = isEmpty;
    this.forEach = forEach;
}