// Sum the stock across every warehouse, skipping any blanks.

async function totalStock(ids) {

  let total = 0;

  const active = ids.filter((id) => id != null);

  active.forEach(async (id) => {

    total += await fetchQty(id);

  });

  return total;

}

// fetchQty("a") -> 2, "b" -> 5, "c" -> 1

totalStock(["a", "b", "c"]).then((t) => console.log(t));

// expected: 8

// actual:   0  (!)