custom-hook-usage.ts

import * as React from 'react';
import useFriendStatus from './useFriendStatus';

interface IUser {
  id: number;
  username: string;
}

const FriendsListItem ({ user }) => {
  // We know this value is a boolean since we defined our hook
  const isOnline = useFriendStatus(user.id);
  return (
    <li>
      <span style={{ backgroundColor: isOnline ? 'green' : 'red }} />
      <span>
        {user.username}
      </span>
    <li>
  );
};

On line 11; hook call should be useFriendStatus instead of userFriendStatus with a reduntant r letter. 

On line 11; hook call should be useFriendStatus instead of userFriendStatus with a reduntant r letter.

Thanks! It's been fixed