How to define private constructors in javascript?

Question

I have defined pure objects in JS which expose certain static methods which should be used to construct them instead of the constructor. How can I make a constructor for my

Answer 1

Another possible simple approach is to use predicate function instead of instanceof. For typescript it can be a type guard and type synonym instead of a class can be exported:

// class is private
class _Score {
  constructor() {}
}

export type Score = _Score

export function isScore(s): s is Score {
  return s instanceof _Score
}