jquery onscreen run offscreen pause

Question

Is there a way to pause a long polling script when someone leaves a page up but is not viewing it? So if I have multiple tabs or windows of the app open only the one I am actively viewing would have the active long polling script running?

This can be broken down into 2 subquestions, 1) Is it possible to detect when a user is no longer viewing a page (and, btw, what is 'viewing'), and 2) Can I use this information to pause a long-polling script (which would vary based on your long polling solution) — Matt, May 02 '11 at 16:17
Related: [Is there a way to detect if a browser window is not currently active](http://stackoverflow.com/questions/1060008/is-there-a-way-to-detect-if-a-browser-window-is-not-currently-active) — Erik, May 02 '11 at 16:45
viewing means does not have focus on that particular window/tab. Long polling wise, I can stop it myself easy if I just have something to trigger to pause/stop until focus is back on that window — David, May 02 '11 at 17:57

score 1 · Answer 1 · edited May 23 '17 at 11:47

Actually there is no efficient way to pause script in javascript. But let me suggest one:

function pausecomp(millis){

    var date = new Date();
    var curDate = null;

    do{ 
        curDate = new Date();
    }while(curDate-date < millis);
}

So this would pause the whole script for a number of milliseconds. However this isn't a good practice.

Javascript allows to setup events to occur after a delay:

setTimeout("alert('hello')",1250);

So when this line of code is reached the setTimeout method calls the alert when 1250 milliseconds are passed.

I hope this information helps you ;)

To detect when mouse leaves the window I have setup a jsfiddle for you: http://jsfiddle.net/xPAwu/1/

Besides there are actually some questions on that on stackoverflow: How can I detect when the mouse leaves the window?

Javascript event when mouse leaves browser window

Your first script will hang the browser. It's dangerous to advice it — Edgar Villegas Alvarado, May 02 '11 at 17:27
I pointed out that he should not use it, I wrote it to point out the contrast — DarkLeafyGreen, May 02 '11 at 17:35

score 0 · Answer 2 · answered May 02 '11 at 16:18

The difficulty here is knowing if the user is actually idle or not. I have used this idleTimer plugin in the past and it seemed to work out pretty well. The author uses a combination of events (mousemove keypress, etc) to decide if the user is active or not.

Edgar Villegas Alvarado · Answer 3 · 2011-05-02T16:36:52.810

You could see how much time the page is idle:

<script>
   $(document).ready(function(){
      var lastEventTime = null;
      //Detect a user interaction
      $(document).bind("mousemove keyup mousewheel", function(event){
         lastEventTime = new Date(); //Store last event time
      });
      setInterval(function(){
         var currentTime = new Date();
         var idleSeconds = (currentTime.getTime() - lastEventTime.getTime())/1000;
         if( idleSeconds > 60) return; //If more than 60 seconds idle, stop polling
         pollingScript(); //Here goes your script
      }, 1000);
   });
</script>

What we're doing, is capture when there's a user interaction (move mouse or press a key). If it didn't happen for a long time (60 seconds in this example), we stop executing our polling script.

Hope this helps

jquery onscreen run offscreen pause

3 Answers3