Capitalizing the first letter of the object key value in json in js

function toUpperCase(jsonObj) { if(typeof(jsonObj)=='object'){ for (var key in jsonObj){ jsonObj[key.substring(0,1).toUpperCase()+key.substring(1)] = jsonObj[key]; delete(jsonObj[key]); } return jsonObj; } return data; }var res; var _data = {"myKey":"myValue"}; res = toUpperCase(_data); console.log(res);//{MyKey: "myValue"}console.log(JSON.stringify(res));//{"MyKey":"myValue"}