Convert seconds into DD:HH:MM:SS format that automatically removes leading values and does not include leading zeroes in the first non-zero value.

secondsToMilitaryTimestamp.js

function secondsToMilitary(seconds) {

    let negative = seconds < 0;
    seconds = Math.abs(Math.floor(seconds));

    /*
    Less than 60 seconds
     */
    if (seconds < 60) {
        return "00:" + ((seconds > 10) ? seconds.toString() : '0' + seconds)
    }

    /*
    Find Days, Hours, Minutes, Seconds
     */
    let DdHhMmSs = [
        Math.floor(seconds / 86400),      // Days
        Math.floor(seconds / 3600) % 24,  // Hours
        Math.floor(seconds / 60) % 60,    // Minutes
        seconds % 60                        // Seconds
    ];

    /*
    Remove leading zeros
     */
    DdHhMmSs = DdHhMmSs.filter(

        // For each entry (Days -> Seconds)
        (number, index, array) => {

            // Check if the ones before it including it are zero
            return !(array.slice(0, index + 1).every((_number) => _number === 0))

        }

    )

    /*
    Convert array to timestamp
     */
    DdHhMmSs = DdHhMmSs.map(

        (number, index) => {

            return (

                // If the item is bigger than 9 or it's the leading number
                (number > 9 || index === 0) ? number.toString() : '0' + number
            )

        }
    )

    // Join with delimiter
    return (negative ? "-" : "") + DdHhMmSs.join(":");




}

/*
Uses an anonymous function, will be slower
 */
const secondsToMilitaryMini = (s) => (s < 0 ? "-" : '') + ((s) => (s < 60 ? "00:" + ((s > 10) ? s.toString() : '0' + s) : ([Math.floor(s / 86400), Math.floor(s / 3600) % 24, Math.floor(s / 60) % 60, s % 60].filter((number, index, array) => !(array.slice(0, index + 1).every((_number) => _number === 0))).map((number, index) => (number > 9 || index === 0) ? number.toString() : '0' + number).join(":"))))(Math.abs(Math.floor(s)));


/*
Faster than the one-liner, for values larger than 0.
 */
function secondsToTimestamp(s) {
    s = Math.floor(s);
    return s < 60 ? "00:" + ((s > 9) ? s.toString() : '0' + s) : (
        [Math.floor(s / 86400), Math.floor(s / 3600) % 24, Math.floor(s / 60) % 60, s % 60]
            .filter((number, index, array) => !(array.slice(0, index + 1).every((_number) => _number === 0)))
            .map((number, index) => (number > 10 || index === 0) ? number.toString() : '0' + number)
            .join(":")
    );
}