js构建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);    }  };  this.arr = new Array();  this.get = get;  this.put = put;  this.remove = remove;}