原生态的js map

<script>
var map = {}; 
map["key1"] = "Value1"; // 加入值对 
map["key2"] = "Value2"; 
map["key3"] = "Value3"; 

for(var k in map) { // 遍历 
  alert(k + " = " + map[k]); 
} 
var mykey="key1";
alert("key1的数值"+map[mykey] );
delete map["key1"]; // 删除

var mykey="key5";
if(mykey in map){//判断是否存在
alert(mykey+"的数值"+map[mykey] );
}else{
alert("不存在"+mykey+"的数值");
}
</script>