Randomize setInterval ( How to rewrite same random after random interval)

Question

I'd like to know how to achieve: generate a random number after a random number of time. And reuse it.

function doSomething(){
     // ... do something.....
}

var rand = 300; // initial rand time

i = setinterval(function(){

     doSomething();
     rand = Math.round(Math.random()*(3000-500))+500; // generate new time (between 3sec and 500"s)

}, rand);

And do it repeatedly.

So far I was able to generate a random interval, but it last the same until the page was refreshed (generating than a different time- interval).

Thanks

Akkuma · Answer 1 · 2011-08-08T14:59:09.637

111

Here is a really clean and clear way to do it:

http://jsfiddle.net/Akkuma/9GyyA/

function doSomething() {}

(function loop() {
    var rand = Math.round(Math.random() * (3000 - 500)) + 500;
    setTimeout(function() {
            doSomething();
            loop();  
    }, rand);
}());

EDIT:

Explanation: loop only exists within the immediately invoked function context, so it can recursively call itself.

edited Aug 08 '11 at 14:59

answered Aug 05 '11 at 21:23

Akkuma

2,215
3
16
21

1

Nice solution, but it requires some change if you want to be able to remove "interval" in a while. – topright gamedev Mar 02 '14 at 15:36
3

@toprightgamedev if you want to stop looping, simply place an if statement around the setTimeout with the logic you need. – Akkuma Oct 22 '15 at 19:00
Sorry to dig up this answer so many year after but I have a question : won't you have a stack of execution context that keep increasing without end with this solution ? – jobou May 23 '17 at 10:52
I found a nice explanation on why it does not create a stack of execution context : https://stackoverflow.com/a/13506904/1951430 – jobou May 23 '17 at 11:00
@jobou it does stack execution contexts. You're right. – user3871 Oct 17 '18 at 04:51
what is the purpose of `(3000 - 500)) + 500`? is this supposed to make it more random? – oldboy Oct 16 '20 at 11:40

jabacchetta · Accepted Answer · 2020-02-19T20:00:44.480

Here's a reusable version that can be cleared. Open-sourced as an NPM package with IntelliSense enabled.

Utility Function

const setRandomInterval = (intervalFunction, minDelay, maxDelay) => {
  let timeout;

  const runInterval = () => {
    const timeoutFunction = () => {
      intervalFunction();
      runInterval();
    };

    const delay = Math.floor(Math.random() * (maxDelay - minDelay + 1)) + minDelay;

    timeout = setTimeout(timeoutFunction, delay);
  };

  runInterval();

  return {
    clear() { clearTimeout(timeout) },
  };
};

Usage

const interval = setRandomInterval(() => console.log('Hello World!'), 1000, 5000);

// // Clear when needed.
// interval.clear();

BrokenGlass · Answer 3 · 2011-08-05T21:23:49.560

7

Something like this should work - use setTimeout() instead so you can set a new random value each time:

function doSomething() {
    alert("doing something");
}

function init() {
    var myFunction = function() {
        doSomething();
        var rand = Math.round(Math.random() * (3000 - 500)) + 500; // generate new time (between 3sec and 500"s)
        setTimeout(myFunction, rand);
    }
    myFunction();
}

$(function() {
    init();
});

Working jsFiddle here.

edited Aug 05 '11 at 21:23

answered Aug 05 '11 at 21:13

BrokenGlass

158,293
28
286
335

@roXon: Yes - that way you can update the random interval each time – BrokenGlass Aug 05 '11 at 21:17
That's jQuery at the end, not plain Javascript. – felwithe May 25 '15 at 13:23
How can you pass arguments with this method? – adrian Oct 06 '18 at 20:15

score 3 · Answer 4 · answered Aug 05 '11 at 21:14

3

Just setup interval each time you rand (and clear it first)

function doSomething(){
     // ... do something.....
}

var i;
var rand = 300;

function randomize() {
    doSomething();
    rand = Math.round(Math.random()*(3000-500))+500; 
    clearInterval(i);
    i = setInterval('randomize();', rand);
}

i = setInterval('randomize();', rand);

or try using setTimeout (and setting again after randing)

answered Aug 05 '11 at 21:14

Nazin

827
3
16
31

2

On a side note it should be `setInterval(randomize, rand);` – Roko C. Buljan Apr 04 '13 at 08:24

score 1 · Answer 5 · answered Nov 03 '16 at 07:50

Just throwing my hat in the ring

    var keepLooping = true;
    (function ontimeout(){
        if(keepLooping){
            doTheAction();
            setTimeout(ontimeout, Math.random() * 100);
        }
    })();

depends if you want to put doTheAction() inside the setTimeout callback or not. I think it's fine to put it before/outside. If you want the initial delay, then put it inside, if not, put it outside for simplicity.

score 0 · Answer 6 · answered Dec 10 '22 at 02:09

I am using this:

function setRandomInterval(intervalFunction, minDelay, maxDelay) {
  let outerFunction = () => {
    let delay = Math.floor(Math.random() * (maxDelay - minDelay + 1)) + minDelay;
    let timeout = setTimeout(outerFunction, delay)
    intervalFunction(timeout)
  }
  outerFunction()
}

Usage:

let start = performance.now()
let i = 1
setRandomInterval((timeout) => {
  let end = performance.now()
  console.log("Run count", i)
  console.log("Random time elapsed", (end - start) / 1000)
  start = end
  i++
  if (i > 5) {
    clearTimeout(timeout)
  }
}, 500, 5000)

Randomize setInterval ( How to rewrite same random after random interval)

6 Answers6

Linked