Home/ Questions/Q 6110959
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-23T14:34:33+00:00

Possible Duplicate: Chrome: timeouts/interval suspended in background tabs? Is there a minimum allowed delay

  • 0

Possible Duplicate:
Chrome: timeouts/interval suspended in background tabs?

Is there a minimum allowed delay for setInterval() and setTimeout() when being run on a tab you’re not currently looking at?

This code runs setInterval() with a specified delay of 100ms and writes out how long the delay actually was. It also reports when you enter/leave the tab.

<html>
<body>
<script type="text/javascript">

window.onfocus = function () { document.body.innerHTML += 'entered tab<br />'; };
window.onblur = function () { document.body.innerHTML += 'left tab<br />'; };
var previous = new Date().getTime();
setInterval(function () {
    var now = new Date().getTime();
    var elapsed = now - previous;
    document.body.innerHTML += elapsed + '<br />';
    previous = now;
}, 100);

</script>
</body>
</html>

Here’s an excerpt of the output on Chrome 12.0.742.100 on Ubuntu 10.04.2 LTS:

101
101
101
left tab
1001
1000
1004
1003
1002
1000
entered tab
101
101
101
102
101

I tried different values for the delay too. Any value less than 1000 results in the same behavior of it being raised to 1000 when you’re looking at a different tab. Values over 1000 behave correctly. And the same thing happens with the setTimeout() version of this code.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    I know your example was for Chrome, but for Firefox at least, from the Firefox 5 Release Notes (under “What’s New in Firefox”).

    Background tabs have setTimeout and
    setInterval clamped to 1000ms to
    improve performance

    Oh, and I just realised this has already been asked in regard to chrome, over here: Chrome: timeouts/interval suspended in background tabs?. There’s a link there that shows that this is also true in Chrome.

    • 0