Is there a more accurate way to create a Javascript timer than setTimeout?

Are there any tricks that can be done to ensure that setTimeout() performs accurately (without resorting to an external API) or is this a lost cause?

No and no. You're not going to get anything close to a perfectly accurate timer with setTimeout() - browsers aren't set up for that. However, you don't need to rely on it for timing things either. Most animation libraries figured this out years ago: you set up a callback with setTimeout(), but determine what needs to be done based on the value of (new Date()).milliseconds (or equivalent). This allows you to take advantage of more reliable timer support in newer browsers, while still behaving appropriately on older browsers.

It also allows you to avoid using too many timers! This is important: each timer is a callback. Each callback executes JS code. While JS code is executing, browser events - including other callbacks - are delayed or dropped. When the callback finishes, additional callbacks must compete with other browser events for a chance to execute. Therefore, one timer that handles all pending tasks for that interval will perform better than two timers with coinciding intervals, and (for short timeouts) better than two timers with overlapping timeouts!

Summary: stop using setTimeout() to implement "one timer / one task" designs, and use the real-time clock to smooth out UI actions.


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REF; http://www.sitepoint.com/creating-accurate-timers-in-javascript/

This site bailed me out on a major scale.

You can use the system clock to compensate for timer inaccuracy. If you run a timing function as a series of setTimeout calls — each instance calling the next — then all you have to do to keep it accurate is work out exactly how inaccurate it is, and subtract that difference from the next iteration:

var start = new Date().getTime(),  
    time = 0,  
    elapsed = '0.0';  
function instance()  
{  
    time += 100;  
    elapsed = Math.floor(time / 100) / 10;  
    if(Math.round(elapsed) == elapsed) { elapsed += '.0'; }  
    document.title = elapsed;  
    var diff = (new Date().getTime() - start) - time;  
    window.setTimeout(instance, (100 - diff));  
}  
window.setTimeout(instance, 100);  

This method will minimize drift and reduce the inaccuracies by more than 90%.

It fixed my issues, hope it helps


I had a similar problem not long ago and came up with an approach which combines requestAnimationFrame with performance.now() which works very effectively.

Im now able to make timers accurate to approx 12 decimal places:

    window.performance = window.performance || {};
    performance.now = (function() {
        return performance.now       ||
            performance.mozNow    ||
            performance.msNow     ||
            performance.oNow      ||
            performance.webkitNow ||
                function() {
                    //Doh! Crap browser!
                    return new Date().getTime(); 
                };
        })();

http://jsfiddle.net/CGWGreen/9pg9L/