How to check if a given value is in a union type array

Question

I have an array of given union type, then wants to check if a string from a superset of the union type is contained in the array (runtime check):

Answer 1

I have found a potentially safer solution to this problem:

const knownStrings = {
  abc: true,
  def: true,
};

const isKnownString = (name: string): name is keyof typeof knownStrings => name in knownStrings;

This doesn't require any typecasting, the only downside is the redundant true values.