转载： js实现map
function Map() { 
var struct = function(key, value) { 
  this.key = key; 
  this.value = value; 
} 
  
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); 
} 
  
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; 
} 
  
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); 
  } 
} 
  
var size = function() { 
  return this.arr.length; 
} 
  
var isEmpty = function() { 
  return this.arr.length <= 0; 
}  
this.arr = new Array(); 
this.get = get; 
this.put = put; 
this.remove = remove; 
this.size = size; 
this.isEmpty = isEmpty; 
} 



var map = new Map(); 
map.put("re","redhacker"); 
map.put("do","douguoqiang"); 
map.put("gq","dougq"); 
alert("map的大小为：" + map.size()) 
alert("key为re的map中存储的对象为：" + map.get("re")); 
map.remove("re"); 
alert("移除key为re的对象后，获取key为re的map中存储的对象为：" + map.get("re")); 
alert("map移除一个元素后的大小为：" + map.size()); 
alert("map是否是一个空map:" + map.isEmpty());