取消订阅PubNub频道以响应（之前）卸载事件

Question

I am building a multi-players game in angular using the PubNub service, including the presence add-on.

Since I need to detect if someone left the game unexpectedly - in order to send a message to the other players and end the game - I am trying to unsubscribe a user when he refreshes the page or goes to some other url. However, in Chrome - as opposed to FireFox - no presence event is being triggered, which probably means that the user wasn't unsubscribed prior to his leaving of the page.

CODE:

 $(window).bind("unload",function(e) {

    PubNub.ngUnsubscribe({channel:$scope.game.channel});
    e.preventDefault();

    }); 

I am aware that these events ( beforeunload and unload ) are problematic and have poor browser support, which is probably the reason for the failure. If this is the case, is there any other cross-browsers detection method I can use?

Answer 1

There is no reliable way to catch the browser closing. The "beforeUnload" event is your best shot, but most mobile browsers don't trigger it. The best way to handle a user closing the browser in PubNub is to specify a heartbeat when subscribing ( http://www.pubnub.com/docs/javascript/api/reference.html#subscribe ). The heartbeat tells how many seconds PubNub should wait after an ungraceful disconnect (such as closing the browser), before considering a user as timed out. This is defaulted to 320 and can be set to as low as 6 seconds (> 5). It still won't be immediate, but you will receive a presence "timeout" action 6 seconds after the browser is closed. Having a low heartbeat could impact your battery life so be wary of that.

Also, I know I linked the doc to the JS API, but the angular ngSubscribe allows most of the same arguments.

Hope that helps.