Serial collection of a SyncOrAsync array applied against a function

thenCollect.ts

export type SyncOrAsync<T> = T | Promise<T>
export type Maybe<T> = T | undefined
export type MaybeSyncOrAsync<T> = Maybe<SyncOrAsync<Maybe<T>>>

/**
 * Serialized promise gathering and compaction
 */
export async function thenCollect<T1, T2>(
  arr: MaybeSyncOrAsync<MaybeSyncOrAsync<T1>[]>,
  f: (t: T1) => MaybeSyncOrAsync<T2>
): Promise<T2[]> {
  const result: T2[] = []
  for (const eaP of toA(await arr)) {
    if (eaP != null) {
      const ea = await eaP
      if (ea != null) {
        const r = await f(ea)
        if (r != null) result.push(r)
      }
    }
  }
  return result
}