[harg]

Sure, if you're validating some data there're loads of better ways to do it than a bunch of conditionals. I was purely commenting on the switch(true) pattern vs some "if"s.

That approach looks nice though. On that subject, JS has some nice libraries including io-ts[1] which has a functional approach using Eithers to encapsulate errors/success.

[1]: https://github.com/gcanti/io-ts

[CloselyChunky]

Sure, if you have an either/result type, the whole thing becomes a fold, where each validator is a function from user to Either<Error, User> and then

  validators.reduce(Either.right(user), (acc, next) -> acc.flatMapRight(next))

This way you'll end up with either the validated user, or the first error that occurred and all the other validators were skipped.