setTimeout with Date object

I'm creating a timeout based on user input, with the input format being: 1min or 2h, and deciding if it's a minute or an hour via the following code;

1min

2h

if (duration.includes("h", 1))
/* If the collectedDuration includes "h" in it,
parse the string into an integer and multiply it with an hour in miliseconds */
const intDuration = parseInt(duration, 10);
const parsedDuration = intDuration * 3600000;
// Create the timer with setTimeout where parsedDuration is the delay
createTimer(item, parsedDuration);
else if (duration.includes("m", 1))
const intDuration = parseInt(duration, 10);
const parsedDuration = intDuration * 60000;
createTimer(item, parsedDuration);



What I want to do: Figure out how much time is left until setTimeout completes at any given time before it does. For example: Timer is created for 1 hour and 15 minutes later, I use a command to display the time left which would be 45 minutes.

I tried the convertion method found here but that is static; it only converts base miliseconds to hours. I need something dynamic.

I have also tried doing it with Date objects but failed. How can I go on about it?

setTimeout

2 Answers
2

You can't do that with vanilla setTimeout. You'll have to wrap it:

setTimeout

class Timeout
// this is a pretty thin wrapper over setTimeout
constructor (f, n, ...args)
this._start = Date.now() + n; // when it will start
this._handle = setTimeout(f, n, ...args);


// easy cancel
cancel ()
clearTimeout(this._handle);


// projected start time - current time
get timeLeft ()
return this._start - Date.now();




I wish they'd provided an OO interface for timeouts/intervals in the first place. Usage:

const timeout = new Timeout(console.log, 2000, 'foo', 'bar');
setTimeout(() => console.log(timeout.timeLeft), 1000);


Should print something like

1000
foo bar


Over the course of a couple of seconds.

This answer is incomplete, more of a suggestion.

You said you failed attempting to do what you need using the Date object, consider whatever that method was using the momentjs library. Moment makes modifying Date considerably easier than converting to epoch then adding/subtracting ms.

https://momentjs.com/

You can do stuff like:

var x = moment(); // sets x to now
x.subtract(10, 'minute'); // subtracts 10 minutes
console.log(x.format('MMMM Do YYYY, h:mm:ss a')); // see what you have now


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