How can I make setInterval also work when a tab is

I have a setInterval running a piece of code 30 times a second. This works great, however when I select another tab (so that the tab with my code becomes inactive), the setInterval is set to an idle state for some reason.

I made this simplified test case (http://jsfiddle.net/7f6DX/3/):

var $div = $('div');
var a = 0;

setInterval(function() {
    a++;
    $div.css("left", a)
}, 1000 / 30);

If you run this code and then switch to another tab, wait a few seconds and go back, the animation continues at the point it was when you switched to the other tab. So the animation isn't running 30 times a second in case the tab is inactive. This can be confirmed by counting the amount of times the setInterval function is called each second - this will not be 30 but just 1 or 2 if the tab is inactive.

I guess that this is done by design so as to improve performance, but is there any way to disable this behaviour? It is actually a disadvantage in my scenario.

标签： javascript google-chrome setinterval

10条回答

何处买醉

2楼-- · 2018-12-31 02:38

Heavily influenced by Ruslan Tushov's library, I've created my own small library. Just add the script in the <head> and it will patch setInterval and setTimeout with ones that use WebWorker.

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唯独是你

3楼-- · 2018-12-31 02:39

I think that a best understanding about this problem is in this example: http://jsfiddle.net/TAHDb/

I am doing a simple thing here:

Have a interval of 1 sec and each time hide the first span and move it to last, and show the 2nd span.

If you stay on page it works as it is supposed. But if you hide the tab for some seconds, when you get back you will see a weired thing.

Its like all events that didn't ucur during the time you were inactive now will ocur all in 1 time. so for some few seconds you will get like X events. they are so quick that its possible to see all 6 spans at once.

So it seams chrome only delays the events, so when you get back all events will occur but all at once...

A pratical application were this ocur iss for a simple slideshow. Imagine the numbers being Images, and if user stay with tab hidden when he came back he will see all imgs floating, Totally mesed.

To fix this use the stop(true,true) like pimvdb told. THis will clear the event queue.

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爱死公子算了

4楼-- · 2018-12-31 02:41

On most browsers inactive tabs have low priority execution and this can affect JavaScript timers.

If the values of your transition were calculated using real time elapsed between frames instead fixed increments on each interval, you not only workaround this issue but also can achieve a smother animation by using requestAnimationFrame as it can get up to 60fps if the processor isn't very busy.

Here's a vanilla JavaScript example of an animated property transition using requestAnimationFrame:

var target = document.querySelector('div#target')
var startedAt, duration = 3000
var domain = [-100, window.innerWidth]
var range = domain[1] - domain[0]

function start() {
  startedAt = Date.now()
  updateTarget(0)
  requestAnimationFrame(update)
}

function update() {
  let elapsedTime = Date.now() - startedAt

  // playback is a value between 0 and 1
  // being 0 the start of the animation and 1 its end
  let playback = elapsedTime / duration

  updateTarget(playback)
  
  if (playback > 0 && playback < 1) {
  	// Queue the next frame
  	requestAnimationFrame(update)
  } else {
  	// Wait for a while and restart the animation
  	setTimeout(start, duration/10)
  }
}

function updateTarget(playback) {
  // Uncomment the line below to reverse the animation
  // playback = 1 - playback

  // Update the target properties based on the playback position
  let position = domain[0] + (playback * range)
  target.style.left = position + 'px'
  target.style.top = position + 'px'
  target.style.transform = 'scale(' + playback * 3 + ')'
}

start()

body {
  overflow: hidden;
}

div {
    position: absolute;
    white-space: nowrap;
}

<div id="target">...HERE WE GO</div>

For Background Tasks (non-UI related)

@UpTheCreek comment:

Fine for presentation issues, but still there are some things that you need to keep running.

If you have background tasks that needs to be precisely executed at given intervals, you can use HTML5 Web Workers. Take a look at Möhre's answer below for more details...

CSS vs JS "animations"

This problem and many others could be avoided by using CSS transitions/animations instead of JavaScript based animations which adds a considerable overhead. I'd recommend this jQuery plugin that let's you take benefit from CSS transitions just like the animate() methods.

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闭嘴吧你

5楼-- · 2018-12-31 02:44

Playing an audio file ensures full background Javascript performance for the time being

For me, it was the simplest and least intrusive solution - apart from playing a faint / almost-empty sound, there are no other potential side effects

You can find the details here: https://stackoverflow.com/a/51191818/914546

(From other answers, I see that some people use different properties of the Audio tag, I do wonder whether it's possible to use the Audio tag for full performance, without actually playing something)

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美炸的是我

6楼-- · 2018-12-31 02:50

I ran into the same problem with audio fading and HTML5 player. It got stucked when tab became inactive. So I found out a WebWorker is allowed to use intervals/timeouts without limitation. I use it to post "ticks" to the main javascript.

WebWorkers Code:

var fading = false;
var interval;
self.addEventListener('message', function(e){
    switch (e.data) {
        case 'start':
            if (!fading){
                fading = true;
                interval = setInterval(function(){
                    self.postMessage('tick');
                }, 50);
            }
            break;
        case 'stop':
            clearInterval(interval);
            fading = false;
            break;
    };
}, false);

Main Javascript:

var player = new Audio();
player.fader = new Worker('js/fader.js');
player.faderPosition = 0.0;
player.faderTargetVolume = 1.0;
player.faderCallback = function(){};
player.fadeTo = function(volume, func){
    console.log('fadeTo called');
    if (func) this.faderCallback = func;
    this.faderTargetVolume = volume;
    this.fader.postMessage('start');
}
player.fader.addEventListener('message', function(e){
    console.log('fader tick');
    if (player.faderTargetVolume > player.volume){
        player.faderPosition -= 0.02;
    } else {
        player.faderPosition += 0.02;
    }
    var newVolume = Math.pow(player.faderPosition - 1, 2);
    if (newVolume > 0.999){
        player.volume = newVolume = 1.0;
        player.fader.postMessage('stop');
        player.faderCallback();
    } else if (newVolume < 0.001) {
        player.volume = newVolume = 0.0;
        player.fader.postMessage('stop');
        player.faderCallback();
    } else {
        player.volume = newVolume;
    }
});

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墨雨无痕

7楼-- · 2018-12-31 02:51

Just do this:

var $div = $('div');
var a = 0;

setInterval(function() {
    a++;
    $div.stop(true,true).css("left", a);
}, 1000 / 30);

Inactive browser tabs buffer some of the setInterval or setTimeout functions.

stop(true,true) will stop all buffered events and execute immediatly only the last animation.

The window.setTimeout() method now clamps to send no more than one timeout per second in inactive tabs. In addition, it now clamps nested timeouts to the smallest value allowed by the HTML5 specification: 4 ms (instead of the 10 ms it used to clamp to).

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