jsp页面定义的map

<script type="text/javascript">
function Map(){
this.elements = new Array();
//删除MAP所有元素
this.clear = function() {
this.elements = new Array();
}

//向MAP中增加元素（key, value)
this.put = function(_key, _value) {
this.elements.push( {
key : _key,
value : _value
});
}

//删除指定KEY的元素，成功返回True，失败返回False
this.remove = function(_key) {
var bln = false;
try {
for (i = 0; i < this.elements.length; i++) {
if (this.elements[i].key == _key) {
this.elements.splice(i, 1);
return true;
}
}
} catch (e) {
bln = false;
}
return bln;
}

//获取指定KEY的元素值VALUE，失败返回NULL
this.get = function(_key) {
try {
for (i = 0; i < this.elements.length; i++) {
if (this.elements[i].key == _key) {
return this.elements[i].value;
}
}
} catch (e) {
return null;
}
}

//判断MAP中是否含有指定KEY的元素
this.containsKey = function(_key) {
var bln = false;
try {
for (i = 0; i < this.elements.length; i++) {
if (this.elements[i].key == _key) {
bln = true;
}
}
} catch (e) {
bln = false;
}
return bln;
}

//获取MAP中所有VALUE的数组（ARRAY）
this.values = function() {
var arr = new Array();
for (i = 0; i < this.elements.length; i++) {
arr.push(this.elements[i].value);
}
return arr;
}

//获取MAP中所有KEY的数组（ARRAY）
this.keys = function() {
var arr = new Array();
for (i = 0; i < this.elements.length; i++) {
arr.push(this.elements[i].key);
}
return arr;
}
}

</script>

<script type="text/javascript">

//------------------------------取map中的元素的key----------------------------------------------------

var map = new Map();

for ( var i = 0 ; i < map.elements.length ; i++ ){
alert("before---"+map.elements[i].key);
}

</script>