async-interval-timer

Use Case

You want some piece of code to run repeatedly, with an n-millisecond wait in between completed runs. The piece of code that you want to run may be asynchronous. Example: every 30 seconds, asynchronously pull an update from a REST API and check for some condition; stop the timer when the condition is true.

Info

The main point of the timer is this: the callback is not guaranteed to be called every n milliseconds, but there is guaranteed to be a wait of n milliseconds between the end of the callback's execution, and the next calling of the callback. Optionally works with asyncawait.

How it Works

Instantiate a Timer instance

• specify an interval (number of milliseconds)
• specify a callback
• specify any other (non-required) options
• start the timer
• stop the timer when desired

Options

runFirst: optionally, call the callback immediately upon starting the timer. Otherwise, the callback will be called for the first time, after one interval duration (the default).

Async Callbacks

Following the asyncawait paradigm, if your callback is an awaitable (async()), you can optionally start the timer with startAsync() instead of start(); this will ensure that the wait interval doesn't start until execution of the async callback is completely done.

Usage:

Instantiation

const Timer = require('async-interval-timer'); 

//prints 'hi' every 1000 ms 
const timer = new Timer(1000, () => { console.log('hi')}); 

// - or - 
const timer = new Timer(1000); 
timer.setCallback(() => { console.log('hi')});

Starting

//if interval && callback already specified 
timer.start();

//if callback not yet specified (or to change it) 
timer.start(() => { console.log('hi')});

//call with 'runFirst' option
timer.start(() => { console.log('hi')}, true);

Change the Interval While Running

//if interval && callback already specified 
timer.start();

//increase interval to every minute
timer.changeInterval(60000);

Stop the Timer

const duration = timer.stop();

console.log ('timer has run for ' + duration + ' ms'); 

Run Async Code

const Timer = require('async-interval-timer'); 

//asynchronous method 
const asyncMethod = async(() => {
    //some asynchronous operation 
});

//call asyncMethod every second
const timer = new Timer(1000, () => asyncMethod);

//start timer 
timer.startAsync(asyncMethod);