@jasonpollman/dynamic-interval

For the rare cases when you might need an interval where the delay between calls is dynamic.
This small utility library exports two functions setDynamicInterval and clearDynamicInterval.

Install

Via NPM:

npm install @jasonpollman/dynamic-interval --save

For the browser:
dist/dynamicInterval.min.js is UMD

<script src="dist/dynamicInterval.min.js"></script>
<script>
  var setDynamicInterval = dynamicInterval.setDynamicInterval;
  var clearDynamicInterval = dynamicInterval.clearDynamicInterval;
</script>

Usage

import { setDynamicInterval } from '@jasonpollman/dynamic-interval';

const baseTimes = [1000, 2000, 3000];

function invervalScheduler(baseTimes) {
  return baseTimes.shift() || 1000;
}

const timerReference = setDynamicInterval(() => console.log('Hello World!'), intervalScheduler));
// Logs "Hello World!" after 1 second, then 2, then 3, then every 1 second.

API

setDynamicInterval({function} callback, {function|Array|number} intervalScheduler, {...any} params) => {object}

Calls callback every intervalScheduler() milliseconds and returns a reference for clearing.

setDynamicInterval takes in two functions: callback and intervalScheduler. All remaining arguments are passed to callback at every invocation.

• callback is called for each tick of the interval.
• intervalScheduler is a method that should return a numeric value (the next delay of the interval).

Note, if intervalScheduler returns a non-numeric or negative value the interval will terminate.
While debatable, this is by design and differs from the behavior of setInterval (which in most cases will use 0 or some other "immediate" value for NaN).

intervalScheduler also supports Array types, which will iterate over each value in the array and terminate when either a non-numeric value is found or all values have been exhausted.

clearDynamicInterval({object} dynamicIntervalReference) => {undefined}

Clears a dynamic interval reference. Softly fails for all other misuse.

Examples

Double Time

Sets an interval that's twice as long as the previous, starting with one second.

let multiplier = 500;

function callback() {
  // Do something...
}

function intervalScheduler() {
  multiplier *= 2;
  return multiplier;
}

setDynamicInterval(callback, intervalScheduler);

Array Based

You can use an array—it will clear the interval once all values have been used once.
Note, the input array is left unmutated.

The following will run 3 times, first after 100ms, then 200ms, then 300ms.
The interval will then be cleared since no items remain in the array.

setDynamicInterval(() => { /* Do something... */ }, [100, 200, 300]);