how to calculate seconds in javascript code example

Example: javascript convert seconds to minutes seconds

function convertHMS(value) {
    const sec = parseInt(value, 10); // convert value to number if it's string
    let hours   = Math.floor(sec / 3600); // get hours
    let minutes = Math.floor((sec - (hours * 3600)) / 60); // get minutes
    let seconds = sec - (hours * 3600) - (minutes * 60); //  get seconds
    // add 0 if value < 10; Example: 2 => 02
    if (hours   < 10) {hours   = "0"+hours;}
    if (minutes < 10) {minutes = "0"+minutes;}
    if (seconds < 10) {seconds = "0"+seconds;}
    return hours+':'+minutes+':'+seconds; // Return is HH : MM : SS
}