TYPESCRIPT

verify if room exists in socket.io

if (io.sockets.adapter.rooms.has(roomIdentifier]) {
  socket.join(roomIdentifier);
} else {
  console.log(socket.id + 'tried to join ' + roomIdentifier + 'but the room does not exist.');
  // Socket.join is not executed, hence the room not created.
};

verify if room exists in socket.io

io.sockets.adapter.rooms.get("room name")