没有运行onbeforeunload的Javascript代码

Question

I have 3 variables to track timespent in the site

 $_SESSION['checkin']; //logged when user first enters the site 
 $_SESSION['loggedAt']; //logged when the user leaves the site
 $_SESSION['timespent']; //time spent in minutes

What I'm trying to do is everytime the user leaves the page, these values are pushed into the database. What I've done is use onbeforeunload.

Below is how I'm using it:

On every page:

 <script type="text/javascript" src="js/storeSession.js"></script>

storeSession.js:

window.onbeforeunload = confirmExit();
  function confirmExit()
  {
        var xhr = new XMLHttpRequest();
        xhr.open('post','../php/storeSession.php',true);
        xhr.send();
        return "Are you sure you want to leave?";
  }

And storeSession.php:

$_SESSION['loggedAt'] = time();
$temptime = (double)$_SESSION['timespent']/60;
$_SESSION['timespent'] = $_SESSION['loggedAt'] - $_SESSION['checkin'];

mysql_select_db($db, $conn) or die(mysql_error()); 

$data = mysql_query("INSERT INTO user (user_id, timespent) VALUES ($tempuser, $temptime) ON DUPLICATE KEY UPDATE timespent = timespent + $temptime")
        or die(mysql_error()); 

$_SESSION['timespent'] = null;
$_SESSION['loggedAt'] = null;
$_SESSION['checkin'] = null;

mysql_close($con);

I can't find the problem and everything seems to be working alright (no errors and such). Does anyone have any idea?

Answer 1

One problem is this line:

window.onbeforeunload = confirmExit();

You called the function and assigned the return value to window.onbeforeunload , instead of assigning the function itself.

Change the line to:

window.onbeforeunload = confirmExit;

...or use a closure.

Also you are making a POST request without sending any data (you didn't pass anything to the first argument of send() ) - you probably want to be making a GET request instead.

Answer 2

You need to remove the parenthese from your onbefore function

window.onbeforeunload = confirmExit;

Also you are ending the session with the XHR call, before the confirm. If the users cancels the unload, he is still logged out.

Answer 3

Have you tried using onunload instead of onbeforeunload . I remember that the latter one is restricted because it could potentially be used to prevent users from exiting page (or even the browser). I am not completly sure, but i think that (most) browsers only read the returned string and ignore the rest.

Also, i have had some problems with on(before)unload actions myself, and solved them by explicitly using synchronous communication with the server (i used jquery + ajax), otherwise the ajax request wasn't completed (though I have no experience with XMLHttpRequest , but i think this option should be comparable)