Add two string time values (HH:mm:ss) with javascript

add_two_times.js

/**
 * Add two string time values (HH:mm:ss) with javascript
 *
 * Usage:
 *  > addTimes('04:20:10', '21:15:10');
 *  > "25:35:20"
 *  > addTimes('04:35:10', '21:35:10');
 *  > "26:10:20"
 *  > addTimes('30:59', '17:10');
 *  > "48:09:00"
 *  > addTimes('19:30:00', '00:30:00');
 *  > "20:00:00"
 *
 * @param {String} startTime  String time format
 * @param {String} endTime  String time format
 * @returns {String}
 */
function addTimes (startTime, endTime) {
  var times = [ 0, 0, 0 ]
  var max = times.length

  var a = (startTime || '').split(':')
  var b = (endTime || '').split(':')

  // normalize time values
  for (var i = 0; i < max; i++) {
    a[i] = isNaN(parseInt(a[i])) ? 0 : parseInt(a[i])
    b[i] = isNaN(parseInt(b[i])) ? 0 : parseInt(b[i])
  }

  // store time values
  for (var i = 0; i < max; i++) {
    times[i] = a[i] + b[i]
  }

  var hours = times[0]
  var minutes = times[1]
  var seconds = times[2]

  if (seconds >= 60) {
    var m = (seconds / 60) << 0
    minutes += m
    seconds -= 60 * m
  }

  if (minutes >= 60) {
    var h = (minutes / 60) << 0
    hours += h
    minutes -= 60 * h
  }

  return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)
}

There is a bug, if you try something like
addTimes('04:35:10', '21:35:10');
you've got 25:70:20

I fix it like it (from 30 line)

res = (minutes / 60) | 0;
hours += res;
minutes = minutes - (60 * res);

And if you need zero when minutes less then 10, like in my case
('0' + minutes).slice(-2);

@grey-mise nice!

hey hi dude i used this for my requirement to add 2 time fields contains only hours and minutes i got issue
below is fix for it

let take like addTimes('04:50', '21:20');

for (var i = 0; i < 2; i++) {
times1[i] = (isNaN(parseInt(times1[i]))) ? 0 : parseInt(times1[i])
times2[i] = (isNaN(parseInt(times2[i]))) ? 0 : parseInt(times2[i])
times[i] = times1[i] + times2[i];
}

        //var seconds = times[2];
        var minutes = times[1];
        var hours = times[0];

        //if (seconds % 60 === 0) {
        //    hours += seconds / 60;
        //}

        if (minutes >= 60) {
            //res = minutes / 60;
            //hours += res;
            //minutes = minutes - (60 * res);
            res = (minutes / 60) | 0;
            hours += res;
            minutes = minutes - (60 * res);

            minutes = minutes < 10 ? "0" + minutes : minutes;

        }


        result = hours + ':' + minutes;

I have updated the gist, now it's more concise and covers more use cases.

Examples:

addTimes('04:20:10', '21:15:10')
// "25:35:20"
addTimes('04:35:10', '21:35:10')
// "26:10:20"
addTimes('30:59', '17:10')
// "48:09:00"
addTimes('00:19:11', '13')
// "13:19:11"

Thanks for your feedback!

There is bug in your code try below

addTimes('19:30:00', '00:30:00')
// "19:60:00"

To correct this add greater than equal to both:
if (seconds >= 60) { var m = (seconds / 60) << 0 minutes += m seconds -= 60 * m }
if (minutes >= 60) { var h = (minutes / 60) << 0 hours += h minutes -= 60 * h }
Result:
addTimes('19:30:00', '00:30:00')
// "20:00:00"

@AjeshM thanks!

Hi, for my use case I needed to add support for 24hour calculation so for instance 11:55 + 14:00 = 01:55. Therfore I added the foolowing statement:

if(hours >= 24){
hours = hours %24;
hours = hours < 0 ? 24 + hours : +hours;
}

I have published https://github.com/joseluisq/timelite
Feedback welcome!

There is a problem when sum more than 99 hours. You can fix just change to -3 (or how many fields you will use, example: if 1000+ hours, you should use -4) in this line: return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)

I think for this return ('0' + hours).slice(-2) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2) you should write this :
hours = (hours < 10) ? 0${hours} : hours
minutes = (minutes < 10) ? 0${minutes} : minutes
seconds = (seconds < 10) ? 0${seconds} : seconds
return ${hours}:${minutes}:${seconds}

because for sum more than 99 hours, result is incorrect

You are missing radis parameter in parse int

If radix is undefined or 0 (or absent), JavaScript assumes the following: If the input string begins with "0x" or "0X", radix is 16 (hexadecimal) and the remainder of the string is parsed. If the input string begins with "0", radix is eight (octal) or 10 (decimal).

Just implement your code in this tools https://vanpariyar.github.io/useful-tools

Thank you so much ...

Thank you!

If there is a need for longer hours, not only 2 digits like in my case, you can change in the return of the hours from split(-2) to split(-3)

return ('0' + hours).slice(-3) + ':' + ('0' + minutes).slice(-2) + ':' + ('0' + seconds).slice(-2)