Question

If I’m writing javascript that contains a lot of intervals, I tend to keep track of them in a array of interval objects

function Interval(id, desc){
 this.id = id;
 this.desc = desc;
}

prototypes etc....

Then I create my interval functions with something like

intervalArray.push(new Interval(setInterval(function, milli),"Demo interval"))   

I know this is verging on OCD, but trust me, it has made problem solving easier as it’s simpler to keep track of the wretched things at the dev tools prompt when you want to clearInterval on one or two of them when running.

So the question…

Given an interval id, is there any way to access its current status?

ie if I have an interval x set to a repeat time of 300000 to fire every five minutes, is there any way to get x.timer, a function that, after one minute would return 60000?

A couple of times now, while debugging, it would have been useful to know how close a given interval was to firing.

I guess I could add another value to my interval object – .lastFired, initiate it with 0 and update it with a timestamp when it fires off but presumably the browser keeps track of intervals somewhere…

Answer 1

You may extend your Interval Function further:

function Interval(fn, desc, ms){
  this.desc = desc;
  this.status = -1;

  var that = this;

  this.id = window.setInterval(function () {

    // save some progess to the Interval object
    // that is used, because in interval callback this === window
    that.status++;

    // now call your function fn, using this === Interval object
    fn.call(that);
  }, ms);

  this.stop = function () {
    if (this.id) {
      window.clearInterval(this.id);
      this.id = 0;
      this.status = -1;
    }
  };
}

// Usage:
var myInterval = new Interval(function () {
  // frequent action

  // this === Interval object instance
  if (this.status === 5) this.stop();
}, "description", 10000);

Now you could also create an onprogress event handler like callback, to get notified if your progress changed. You also may move the this.id = window.setInterval(... statement into a this.start = function () { public function, to start and stop later.