现在有个Json对象，但是不知道key是什么，怎么能取到他的key
如：
{"id1"：{"name":"张三","sex":"男"},"student2"：{"name":"老四","sex":"女"},"id3"：{"name":"王五","sex":"男"}}目前不知道这个id是多少，我怎么才能取得这个key，也就是，id1，id2，id3
如：
{"id1"：{"name":"张三","sex":"男"},"student2"：{"name":"老四","sex":"女"},"id3"：{"name":"王五","sex":"男"}}目前不知道这个id是多少，我怎么才能取得这个key，也就是，id1，id2，id3
<script type="text/javascript">
var json={
"id1":{"name":"张三","sex":"男"},
"student2":{"name":"老四","sex":"女"},
"id3":{"name":"王五","sex":"男"}
} ;
recurJson(json);
function recurJson(json)
{
for(var i in json){
document.write(i+":"+json[i]+"<br>");
if(typeof json[i]=="object"){
recurJson(json[i]);
}
}
}
</script>
<html>
<head>
<title>key value</title>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
var a = {name: "wang", sex:"M", age: 21};
$.each(a ,function(i){
alert(a[i]);// wang M 21
alert(i);// name sex age
});
</script>
</head>
<body></body>
</html>
var dat={
"id1":{
"name":"张三",
"sex":"男"},
"id2":{
"name":"老四",
"sex":"女"},
"id3":{
"name":"王五",
"sex":"男"}};
for ( var id in dat ){
alert(id);
}