Accurate Javascript setInterval replacement

interval.js

function interval(duration, fn){
  var _this = this
  this.baseline = undefined
  
  this.run = function(){
    if(_this.baseline === undefined){
      _this.baseline = new Date().getTime()
    }
    fn()
    var end = new Date().getTime()
    _this.baseline += duration
 
    var nextTick = duration - (end - _this.baseline)
    if(nextTick<0){
      nextTick = 0
    }
    
    _this.timer = setTimeout(function(){
      _this.run(end)
    }, nextTick)
  }

  this.stop = function(){
    clearTimeout(_this.timer)
  }
}

This code snippet can be used when a very accurate setInterval is needed. It will always be accurate ( 1+-ms in variance, but the mean will be the exact duration). Of course the function provided must run faster than the duration parameter. If for some reason the function takes more time than the duration in some occasions, the timer will still converge to the exact intervals very fast.

Example of use:

var timer = new interval(50, function(){
      console.log(new Date().getTime())
    })
    timer.run()

Did you snag this from another programming language?

I did not, but this was written when I was quite new in javascript. I have a better version of this code in our framework: https://github.com/OptimalBits/ginger/blob/master/ginger.js

But of course it depends on other things, it is not lightweight as the one in the gist. In any case I am planing a new interval/timer that is a bit more powerful, I want to be able to keep just one timer for all the intervals instances.

on line 20 shouldn't be

})(this)

instead of

}(this))

?

You are tight ezabba

right*

@manast - I've implemented a new version of this at https://gist.github.com/4215634

Rather than calculate the difference between an updated baseline, this instead takes a start time and current time, and calculates a pretty accurate tick value to compensate for drift - I've had this running for hours and keep accurate to within 1-5ms.

A bonus of this version if you use the default 1000ms (1s) tick value, it also gives you an accurate H/M/S timing, as shown in the timer example

This has a problem, when the window lose the focus, the timers speed up after focus again.

Good code, integrated it and works perfect!

@manast
I would add

timer && timer.run();

Why? Consider the code below:

        var si = new interval(50, function () {
                if ("undefined" !== typeof hiddenPreloadImage && hiddenPreloadImage && 0 !== si) {
                    si.stop(),
                    si = 0;
                    setStyleOpacity(superbox, 1),
                    setImmediate(function () {
                        window.progressBar && (progressBar.finish(), progressBar.hide());
                    });
                }
            });
        si && si.run();

I never thought that JavaScript setInterval wasn't perfectly accurate. I applied interval.js in my website and it worked perfectly. Thank you!

I never thought that JavaScript setInterval wasn't perfectly accurate. I applied interval.js in my website and it worked perfectly. Thank you!

try creating a metronome and you'll soon find out how inaccurate it is ;)
http://music.lighting/Metronome/

I am trying to implement this but it does not stop when this.interval.stop() is called, is there any reason why this could be? I am creating it with: that = this;
this.interval = new interval(that.state.timerint, function(){
that.noMetCount()
})

@morganruffner try the latest version instead. I just updated the code.

@manast Unfortunately I still haven't been able to get it to work, I see that it is going into the stop function but the function continues being called.

I am trying to implement this but it does not stop when this.interval.stop() is called, is there any reason why this could be? I am creating it with: that = this;
this.interval = new interval(that.state.timerint, function(){
that.noMetCount()
})

function interval(duration, fn){
  var _this = this
  _this.baseline = undefined
  
  _this.run = function(){
    if(_this.baseline === undefined){
      _this.baseline = new Date().getTime()
    }
    fn()
    _this.end = new Date().getTime()
    _this.baseline += duration
 
    _this.nextTick = duration - (_this.end - _this.baseline)
    if(_this.nextTick<0){
      _this.nextTick = 0
    }

    if (_this.run !== undefined) {
      _this.timer = setTimeout(function(){
        _this.run()
      }, _this.nextTick)
    }
  }

  _this.stop = function(){
    clearTimeout(_this.timer);
    _this.run = undefined;
  }

This works for me. What I assume has happened was, you were trying to call this.interval.stop() inside fn(), but in this case _this.run() will keep executing and creating a new setTimeout and assigned to _this.timer. To counter this, I marked _this.run as undefined in _this.stop, and before the assignment for _this.timer in the _this.run, I check if _this.run is still defined.

I hope this works for other people as well... Please correct me if I'm wrong.

In the first time,it wait double douration, there is the fixed version and with the args:

export function Interval(fn,duration,...args){
    const _this = this;
    this.baseline = undefined

    this.run = function(flag){
        if(_this.baseline === undefined){
            _this.baseline = new Date().getTime() - duration
        }
        if (flag){
            fn(...args);
        }
        const end = new Date().getTime();
        _this.baseline += duration

        let nextTick = duration - (end - _this.baseline);
        if(nextTick<0){
            nextTick = 0
        }

        console.log(nextTick);
        _this.timer = setTimeout(function(){
            _this.run(true)
        }, nextTick)
    }

    this.stop = function(){
        clearTimeout(_this.timer)
    }
}

Great tool!
Might want to have a look at https://github.com/docjojo/Timers