Question

I have a simple JS timer which runs every 10 seconds and should send an AJAX request. The problem is that on some windows XP machines this task stops running – no AJAX request is sent. It seems to run successfully for 45 minutes and then stop for a random amount of time, then start and run successfully for another 45 minutes…my question is what could be causing this to happen? Could some service/scheduled task running on the PC stop javascript timers from working?

Ext.onReady(function(){

    var task = {
        run: function(){
            Ext.Ajax.request({
                url: 'test.php'
            });
        },
        interval: 10000
    };
    Ext.TaskManager.start(task);    

});

Answer 1

Couple of suggestions:

1. Try to switch from Ext.TaskManager to a normal setInterval. If that fixes the problem there’s probably a bug in Task Manager.

2. If it doesn’t work then try the following:

   • Keep using intervals. Record the id of the interval. Also record the time of last execution.

   • Start another timer with setInterval and larger interval, say 1 minute. Inside the callback check for the last execution time.

   • If it was long ago (> 30 seconds), call clearInterval with the id that you stored and restart the task interval.

3. If that doesn’t work try executing these polling tasks in a separate <iframe>. A browser can skip calling Interval and Timeout callbacks if it’s busy with other tasks. By putting them into a separate <iframe> you give them a dedicated event loop, so that other tasks won’t interfere with them.