How to subtract 10 seconds from a specific given timestamp JS

Question

Here is the time:

01:02:25,369

I want to subtract 10 seconds from it, so the return value should be:

01:02:15,369

I know I have to write a function to do so, but things get difficult when seconds are <10 so you have to subtract minutes and hours as well.

How could I convert it to a date ? it is a string and I have no Idea. I got NaN — moemous, Nov 27 '21 at 21:45

score 2 · Answer 1 · answered Nov 27 '21 at 21:37

2

Turn it into a Date, then subtract 10000 (don't reinvent the wheel)

answered Nov 27 '21 at 21:37

April

94
4

1

How could I convert it to a date ? it is a string and I have no Idea. I get NaN – moemous Nov 27 '21 at 21:45
@moemous https://stackoverflow.com/questions/28002261/parse-date-time-string-in-javascript-which-are-of-custom-format – April Nov 27 '21 at 21:52
1

@Puyo the example you cited uses `momentjs`, which is heavy and outdated – skara9 Nov 27 '21 at 21:58
@skara9 i didn't link a specific answer, just linked the question :p – April Nov 27 '21 at 22:02

skara9 · Accepted Answer · 2021-11-27T21:53:16.547

You could just convert it to milliseconds and then add or subtract however much you want. And then make a render function to convert it back into a string if you need it.

function getTotalMS(timeString) {
    const [hms, ms] = timeString.split(',');
    const [h, m, s] = hms.split(':');

    return parseInt(ms) * 1 +
           parseInt(s) * 1000 +
           parseInt(m) * 60 * 1000 +
           parseInt(h) * 60 * 60 * 1000;
}

function renderTime(ms) {
    const h = Math.floor(ms / (60 * 60 * 1000)); ms -= h * 60 * 60 * 1000;
    const m = Math.floor(ms / (60 * 1000)); ms -= m * 60 * 1000;
    const s = Math.floor(ms / (1000)); ms -= s * 1000;

    return `${h<10?'0':''}${h}:${m<10?'0':''}${m}:${s<10?'0':''}${s},${ms}`;
}


// subtracting 10 seconds
let totalTime = getTotalMS('01:02:25,369');
totalTime -= 10 * 1000;
console.log(renderTime(totalTime));

probably could be optimized, but here's a starting point

How to subtract 10 seconds from a specific given timestamp JS

2 Answers2