Handling Missing, Null, Undefined, and Empty Strings with Default Values in TypeScript Structs

export const DEFAULT_TIMEZONE = 'America/New_York';

const EmptyToDefault = S.transform(S.String, S.String, {
  strict: true,
  decode: str => (str.length === 0 ? DEFAULT_TIMEZONE : str),
  encode: identity
});

export const MyStruct = S.Struct({
  timezone: S.optionalWith(EmptyToDefault, {
    nullable: true,
    default: () => DEFAULT_TIMEZONE
  })
  // ...
});

// ...
timezone: S.optionalWith(S.String, {
  emptyAsMissing: true,
  nullable: true,
  default: () => DEFAULT_TIMEZONE
})
// ...