AA4-async-best.js

const getAvatars = async (userId) => {
  const user = await getUser(userId);
  const [avatar, friends] = await Promise.all([user.avatar(), user.friends()])
  const avatars = [avatar];
  
  return avatars.concat(
    await Promise.all(
      friends.map(friend => friend.avatar())
    )
  );
}