server/www/connect.js

window.addEventListener('load', function() {
  var ws = new WebSocket('ws://' + window.location.hostname + '/play/');
  var sessionKey = null;
  var lib = Lib(ws);
  var room = Room(document.getElementById('room'), lib);
  var login = Login(document.getElementById('login'), lib);
  var debug = document.getElementById('debug');
  setTimeout(ping, 20000);

  ws.addEventListener('message', function(event) {
    var o = JSON.parse(event.data);
    switch(o.tag) {
      case "Welcome":
        sessionKey = o.key;
        room.populate(o.room, sessionKey);
        break;
      case "Pong":
        setTimeout(ping, 10000);
        break;
      case "Relay":
        relayedMessage(o)
        break;
      default:
        debug.textContent = event.data;
    }
  });

  function relayedMessage(o) {
    switch(o.message.tag) {
      case "LogIn":
        room.enter(o.from, o.message.name);
        if(o.from == sessionKey) {
          login.on(o.from);
        }
        break;
      case "LogOut":
        room.leave(o.from);
        if(o.from == sessionKey) {
          login.off(o.from);
        }
        break;
      case "Invitation":
        var name = room.name(o.from);
        var accept = false;
        // invitations should come only from known players, in doubt say «no»
        if(name) {
          accept = confirm(name + " has invited you to a game");
        }
        lib.send({tag: "Answer", accept: accept});
    }
  }

  function ping() {
    lib.send({tag: "Ping"});
  }
});