Handling browser window close in a nowjs chat application

Question

I am creating a chat application with nowjs.User can create a chatroom and then invite users to that room.Following is the code used to do this:

everyone.now.addPeopleToChat = function(clientIds,roomName) {
    var length = clientIds.length;
    var group = nowjs.getGroup(roomName);
    for(var i=0;i<length;i++){
        group.addUser(clientIds[i]);
    }
    group.now.roomName = roomName;//User can be in one room only at any given time.Reference to the roomname to be used when user leaves chat
    group.now.loadChatWindow();//Load UI
}

So far so good.Users are able to be added to chat room and chatting is also fine.

When a user is in a chat room and he closes the browser window,I want other users in the chat room to be made aware that this person has left the chat.I thought of using the disconnect event to handle this particular situation.This is the code I have used.

nowjs.on('disconnect', function () {
    console.log("User name:"+this.now.name);//comes fine
    console.log("Room name:"+this.now.roomName);//shows undefined.
    var group = nowjs.getGroup(this.now.roomName);//Intention is to get the room in which user was chatting.But it is not working because roomName is undefined.
    group.now.broadcast(this.now.name+" has left this room");
});

Why is that roomName is shown as undefined in disconnect handler.I am setting that variable when the users are added to the group right.So each of the user in the group should have that variable set right.Am I missing something here?