Rename key inside Object {}

Yes, you can change it, try below code.

if (email !== username ) { Object.defineProperty(obj, username , Object.getOwnPropertyDescriptor(obj, email)); delete obj[email];}

Using ‘defineProperty’, you can update your key name easily. 

If you are using > ES6 then you can achieve it with single line approach.

delete Object.assign(obj, {[username]: obj[email] })[email];

Try any of above two solution, it will rename your key name for sure.

delete Object.assign(obj, {[username]: obj[email] })[email];

This approach works, and it is optimized way to achieve my questions.