@marianmeres/ticker

Do something when it ticks. With a store compatible API.

Under the hood it uses recursive setTimeout with interval corrections, so it should guarantee the precise frequency except for the edge cases where the synchronous subscriber's work cannot keep up with the interval - it will never tick sooner before it finishes.

Install

$ npm i @marianmeres/ticker

Usage

import { createTicker } from '@marianmeres/ticker';

// once started, will tick every 1000 milliseconds
// (interval = 1000, start = false): Ticker
const t = createTicker(1_000);

// basic control api
t.start();
t.stop();

// decrease/increase frequency on existing instance
t.setInterval(ms);

// subscribe api
const unsub = t.subscribe((timestamp) => {
	if (timestamp) {
		// do something on tick
	} else {
		// ticker is stopped (or has not started yet)
	}
});

Delayed Worker Ticker

Using a tick signal from a sync ticker shown above for a periodical asynchronous work (e.g. periodical api data fetching) may not be the best choice. For such cases, use its "delayed" sibling. Instead of frequency, it guarantees a delay between worker calls.

Delayed Worker Ticker Usage

import { createDelayedWorkerTicker } from '@marianmeres/ticker';

// once started, it will do the work, then pause for 1 second, then repeat...
// (worker: CallableFunction, interval = 1000, start = false): DelayedWorkerTicker
const t = createDelayedWorkerTicker(async () => fetch('/api'), 1_000);

// control api
t.start();
t.stop();
t.setInterval(ms);

// subscribe api
const unsub = t.subscribe(({ started, finished, error, result }) => {
	// both `started` and `finished` are timestamps (or zero)
	if (started && !finished) {
		// worker's work is in progress
	} else if (started && finished) {
		// do something with `result` or `error`
	} else {
		// ticker is stopped (or has not started yet)
	}
});

Interval value as a function

If desired, you can define the interval value as a function which returns the number of ms.

type Interval = number | ((previous: number) => number);