Helpers functions for Promises

promises.ts

export const isRejected = (
  input: PromiseSettledResult<unknown>,
): input is PromiseRejectedResult => input.status === 'rejected';

export const isFulfilled = <T>(
  input: PromiseSettledResult<T>,
): input is PromiseFulfilledResult<T> => input.status === 'fulfilled';