Changing the interval of SetInterval while it'

Question

I have written a javascript function that uses setInterval to manipulate a string every tenth of a second for a certain number of iterations.

function timer() {
    var section = document.getElementById('txt').value;
    var len = section.length;
    var rands = new Array();

    for (i=0; i<len; i++) {
        rands.push(Math.floor(Math.random()*len));
    };

    var counter = 0
    var interval = setInterval(function() {
        var letters = section.split('');
        for (j=0; j < len; j++) {
            if (counter < rands[j]) {
                letters[j] = Math.floor(Math.random()*9);
            };
        };
        document.getElementById('txt').value = letters.join('');
        counter++

        if (counter > rands.max()) {
            clearInterval(interval);
        }
    }, 100);
};

Instead of having the interval set at a specific number, I would like to update it every time it runs, based on a counter. So instead of:

var interval = setInterval(function() { ... }, 100);

It would be something like:

var interval = setInterval(function() { ... }, 10*counter);

Unfortunately, that did not work. It seemed like "10*counter" equals 0.

So, how can I adjust the interval every time the anonymous function runs?

Answer 1

You could use an anonymous function:

var counter = 10;
var myFunction = function(){
    clearInterval(interval);
    counter *= 10;
    interval = setInterval(myFunction, counter);
}
var interval = setInterval(myFunction, counter);

UPDATE: As suggested by A. Wolff, use setTimeout to avoid the need for clearInterval.

var counter = 10;
var myFunction = function() {
    counter *= 10;
    setTimeout(myFunction, counter);
}
setTimeout(myFunction, counter);

Answer 2

This is my way of doing this, i use setTimeout:

var timer = {
    running: false,
    iv: 5000,
    timeout: false,
    cb : function(){},
    start : function(cb,iv){
        var elm = this;
        clearInterval(this.timeout);
        this.running = true;
        if(cb) this.cb = cb;
        if(iv) this.iv = iv;
        this.timeout = setTimeout(function(){elm.execute(elm)}, this.iv);
    },
    execute : function(e){
        if(!e.running) return false;
        e.cb();
        e.start();
    },
    stop : function(){
        this.running = false;
    },
    set_interval : function(iv){
        clearInterval(this.timeout);
        this.start(false, iv);
    }
};

Usage:

timer.start(function(){
    console.debug('go');
}, 2000);

timer.set_interval(500);

timer.stop();

Answer 3

A much simpler way would be to have an if statement in the refreshed function and a control to execute your command at regular time intervals . In the following example, I run an alert every 2 seconds and the interval (intrv) can be changed dynamically...

var i=1;
var intrv=2; // << control this variable

var refreshId = setInterval(function() {
  if(!(i%intrv)) {
    alert('run!');
  }
  i++;
}, 1000);

Answer 4

I'm a beginner in javascript, and didn't found any help in the previous answers (but many good ideas).
This piece of code below accelerates (acceleration > 1) or decelerates (acceleration <1). I hope it might help some people:

function accelerate(yourfunction, timer, refresh, acceleration) {
    var new_timer = timer / acceleration;
    var refresh_init = refresh;//save this user defined value
    if (refresh < new_timer ){//avoid reseting the interval before it has produced anything.
        refresh = new_timer + 1 ;
    };
    var lastInter = setInterval(yourfunction, new_timer);
    console.log("timer:", new_timer);
    function stopLastInter() {
        clearInterval(lastInter);
        accelerate(yourfunction, new_timer, refresh_init, acceleration);
        console.log("refresh:", refresh);
    };
    setTimeout(stopLastInter, refresh);
}

With :

• timer: the setInterval initial value in ms (increasing or decreasing)
• refresh: the time before a new value of timer is calculated. This is the step lenght
• factor: the gap between the old and the next timer value. This is the step height

Answer 5

I like this question - inspired a little timer object in me:

window.setVariableInterval = function(callbackFunc, timing) {
  var variableInterval = {
    interval: timing,
    callback: callbackFunc,
    stopped: false,
    runLoop: function() {
      if (variableInterval.stopped) return;
      var result = variableInterval.callback.call(variableInterval);
      if (typeof result == 'number')
      {
        if (result === 0) return;
        variableInterval.interval = result;
      }
      variableInterval.loop();
    },
    stop: function() {
      this.stopped = true;
      window.clearTimeout(this.timeout);
    },
    start: function() {
      this.stopped = false;
      return this.loop();
    },
    loop: function() {
      this.timeout = window.setTimeout(this.runLoop, this.interval);
      return this;
    }
  };

  return variableInterval.start();
};

Example use

var vi = setVariableInterval(function() {
  // this is the variableInterval - so we can change/get the interval here:
  var interval = this.interval;

  // print it for the hell of it
  console.log(interval);

  // we can stop ourselves.
  if (interval>4000) this.stop();

  // we could return a new interval after doing something
  return interval + 100;
}, 100);  

// we can change the interval down here too
setTimeout(function() {
  vi.interval = 3500;
}, 1000);

// or tell it to start back up in a minute
setTimeout(function() {
  vi.interval = 100;
  vi.start();
}, 60000);

Answer 6

(function variableInterval() {
    //whatever needs to be done
    interval *= 2; //deal with your interval
    setTimeout(variableInterval, interval);
    //whatever needs to be done
})();

can't get any shorter