slurmulon / stateful-dynamic-interval

:clock1: The stateful dynamic interval

stateful-dynamic-interval

🕐 The stateful dynamic interval

---

A pauseable and resumeable setInterval built around dynamic-interval

Install

npm install --save stateful-dynamic-interval

then

import setStatefulDynterval from 'stateful-dynamic-interval'

or

import { StatefulDynterval } from 'stateful-dynamic-interval'

Usage

import { StatefulDynterval } from 'stateful-dynamic-interval'

const timer = new StatefulDynterval(context => console.log('tick', context), 1000)

timer.pause()
// ...
timer.resume()

You may also customize the underlying timer and can change the duration of the interval on each tick.

Check out the dynamic-interval package for more details.

Example

This script doubles the amount of time between intervals on each iteration, starting with 50ms.

import { StatefulDynterval } from 'stateful-dynamic-interval'

const timer = new StatefulDynterval(context => ({ wait: context.wait * 2 }), 50)

setTimeout(() => {
  timer.pause()

  setTimeout(() => {
    // this resumed step will only run for the remaining time in the interval,
    // which may be dynamic, meaning it can change on each iteration based on
    // the return value of the callback function (this example is dynamic)
    timer.resume()
  }, 1000)
}, 1000)

Interface

setStatefulDynterval(step, config, api)

• step: The function to call on each interval tick
• config: A dynamic-interval configuration object
• api An optional custom timing API

.run()

Starts the interval. Instantiated StatefulDyntervals will automatically call run unless the lazy config property is set to true.

• Alias: play

.clear()

Stops or clears out the interval. Once an interval has been cleared it cannot be resumed.

• Alias: stop

.pause()

Pauses the interval so that it can be resumed at a later point.

.resume()

Resumes a previously paused interval.

.add(interval)

Synchronizes the parent interval with a child interval.

Child intervals automatically subscribe to the following topics of their parents:

• run
• clear
• pause
• resume

.detach()

Desynchronizes a parent interval from all of its children by unsubscribing them from their parent topics.

License

MIT

stateful-dynamic-interval's Issues

[Enhancement] Improve accuracy of interval

Problem

The accuracy of setInterval is not guaranteed, and this is a problem in many different applications (e.g. trying to align audio playback with other events)

Replace the use of setInterval with this: https://gist.github.com/manast/1185904

Research

• https://stackoverflow.com/questions/27162254/web-workers-setinterval-and-settimeout-reliability
• https://johnresig.com/blog/analyzing-timer-performance/

[Bug] Support interrupting resume of a pause (?)

If you pause an interval and then resume it, that resumption (setTimeout) could take a decent amount of time to complete. If the interval was say 5 seconds, and you paused halfway through, you have 2.5 seconds until the next step runs (i.e. resumes)

The problem here is that somebody might pause again WHILE you're already resuming from another pause, and the setTimeout currently being used right now cannot be interrupted.

resume essentially puts the user into a temporary limbo state where the interval can't be paused.

This could easily get pretty messy and add a bit more complexity, so this requires more thought.

Question, can you run out of stack space?

I'm not sure how this package is implemented, but is it possible for the interval to run indefinitely with no issues?

[Feature] Support hierarchical intervals

It would be nice if you could group intervals together in a hierarchical fashion (DAG).

Resuming, pausing or stopping a parent interval would be reflected in any child intervals.

It would be nice to support bi-directional subscriptions built around EventEmitter, but this can be addressed in a subsequent issue.

This feature should also fix #1, as the resume timer can simply be a child of the parent interval.

[Bug] Action method cannot be an async generator

Example

import { setStatefulDynterval } from 'stateful-dynamic-interval'
import axios from 'axios'

setStatefulDynterval(async ctx => {
  await axios.get('https://reqres.in/api/users')

  return ctx
})

Result

Causes an infinite loop/recursion