If it's multiplayer, you could use Node along with something like socket.io to handle real time communication between players.

You could maybe, possibly, use WebRTC for peer-to-peer communication if you don't mind excluding anyone running Safari and IE. But with a game written in JS and running in the browser, it seems like it would be too easy for someone to modify the code and cheat without a server side component at least trying to verify that everyone is behaving.