js中json对象key值首字母大写化

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"}