const users = [] const addUser = ({id, name, room}) => { const numberOfUsersInRoom = users.filter(user => user.room === room).length if(numberOfUsersInRoom === 2) return { error: 'Room full' } const newUser = { id, name, room } users.push(newUser) return { newUser } } const removeUser = id => { const removeIndex = users.findIndex(user => user.id === id) if(removeIndex!==-1) return users.splice(removeIndex, 1)[0] } const getUser = id => { return users.find(user => user.id === id) } const getUsersInRoom = room => { return users.filter(user => user.room === room) } module.exports = { addUser, removeUser, getUser, getUsersInRoom }