从你的评论中，

例如，这些内部键将失败
{name：john，Age：21，sex：male， place：{state：ca}}

您可能需要对此类情况使用递归。见下文，

  var output = { }; 
 for（i in obj）{
 output [i.toUpperCase（）] = obj [i]; 
} 
 

Is there a way to change all JSON key names to capital letter ?

eg: {"name":"john","Age":"21","sex":"male","place":{"state":"ca"}}

and need to be converted as

{"NAME":"john","AGE":"21","SEX":"male","PLACE":{"STATE":"ca"}}

Thanks in advamnce.

-Navin

From your comment,

eg like these will fail for the inner keys {"name":"john","Age":"21","sex":"male","place":{"state":"ca"}}

You may need to use recursion for such cases. See below,

DEMO

var output = allKeysToUpperCase(obj);

function allKeysToUpperCase(obj) {
    var output = {};
    for (i in obj) {
        if (Object.prototype.toString.apply(obj[i]) === '[object Object]') {
            output[i.toUpperCase()] = allKeysToUpperCase(obj[i]);
        } else {
            output[i.toUpperCase()] = obj[i];
        }
    }
    return output;
}

Output

---

A simple loop should do the trick,

DEMO

var output = {};
for (i in obj) {
   output[i.toUpperCase()] = obj[i];
}