Javascript - Difference dates with 120s - momentjs

Question

I need to show difference between now and now+120 seconds. I need too compare difference in seconds, not in minutes. The code looks like
this.nextDate = moment().add(120, 'seconds');
this.timer = setInterval(() => {
this.currentDate = moment();
this.diff = moment.duration(this.nextDate.diff(this.currentDate));
}, 1000)
The problem: Console.log(this.diff.seconds()) return that difference is 60 seconds (and going down), not 120.
So: What´s the problem? Why moment.js doesn´t get 120s?

Answer 1

There are two problem:
In moment.duration() if you pass just one parameter by default it is the number of milliseconds, so you can moltiply the number for 1000 (moment.duration(diff * 1000)) or you can pass a second parameter indicating the type of time unit like this moment.duration(diff, 'seconds') or passing an object instead of two paramters like moment.duration({ seconds: diff }).
the second problem is the function for extract the seconds from the duration object, you used .seconds() that it return a number between 0 and 59, if you want the length of the duration in seconds you must use .asSeconds()
For me the duration it's a plus in this case, you can use a simple countdown of second like that:
const nextDate = moment().add(120, 'seconds');
const timer = setInterval(() => {
const currentDate = moment();
const seconds = nextDate.diff(currentDate, 'seconds');
console.log(seconds);
}, 1000)
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>
Else you want or you need to use duration this is the code:
const nextDate = moment().add(120, 'seconds');
const timer = setInterval(() => {
const currentDate = moment();
const seconds = nextDate.diff(currentDate, 'seconds');
const duration = moment.duration(nextDate.diff(currentDate, 'seconds'), 'seconds'); // Alternatively const duration = moment.duration({ seconds });
console.log('duration: ', duration.asSeconds());
}, 1000)
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.1/moment.min.js"></script>