Programming

More or less the same but the user gets passed as a method parameter each time. Validators would be in my opinion a long function inside the service also with named variables like this because it's just easy to read and there are no surprises. I'd probably refactor it at around 5 conditions or 30 lines of validation logic.

I recommend trying out using the constructor in services for tools such as a database and methods for data such as user. It will be very easy to use everywhere and for many users and whatever

const passwordIsValid = ...
if (!passwordIsValid){
  return whatever
}