How to sync with server and clear session before the user leaves a page?

Question

Is there any way to detect when a user leaves a page, no matter if it's by closing the browser, entering a new URL in the address bar, clicking on a link that redirects to other domain, etc. ?

The main purpose of this would be to perform some activities such as:

sync with the server some data that resides in the client side
clear server session

I was trying with the window's unload and beforeunload events, and reading other questions like: Best way to detect when a user leaves a web page? // Is there any way to know that user leaving a page with asp.net? but I didn't find the answer I would expect.

Here is a simplified js snippet to understand what I was trying:

window.onunload = function(){
    if (theConditionThatINeed){
        doThings();
        SyncWithServerAndAbandonSession(url, localObjects);
    }
    else {
        doNothing();
    }
}

I don't want to display any kind of confirmation before the user leaves, so I think that the onbeforeunload won't help me here.

Supposing that the answer is "there is no way to do such thing", what would be the recommended practice to accomplish the synchronization and session clearing that I want?

The primary browser that I support is IE >= 7

score 1 · Answer 1 · answered Oct 13 '11 at 16:09

As you already read, it is not reliably possible to detect whether the user leaves your page. Generally it is not good practice to store any unsynced state on the client side. Browsers are easily closed or crashed.

You can send yourself ajax keepalive messages via javascript, in case the user does anything on your page. Again, very unreliable, wasteful and hacky. Auto-Sync after a short timeout.

Take a look at RESTful web applications. The concept is interesting, and, very superficially spoken, discourages keeping state information on the server. You can apply this to the client as well.

This usually results in keeping state information in the URL. The URL tells the server anything it needs to know to service the request, it should not need a memory (the session) of any previous activity. I try to only keep the user identification info in the session. I would get rid of this too, but some tools and libs need the user in the session.

How to sync with server and clear session before the user leaves a page?

1 Answers1