Javascript 在nowjs聊天应用程序中处理浏览器窗口关闭

我正在使用nowjs创建聊天应用程序。用户可以创建聊天室，然后邀请用户访问该聊天室。以下是用于执行此操作的代码：

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
}

为什么断开连接处理程序中的roomName显示为未定义。当用户被添加到组中时，我正在设置该变量。因此组中的每个用户都应该将该变量设置为正确。我是否遗漏了什么

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");
});