Answer by powtac for JavaScript seconds to time string with format hh:mm:ss

String.prototype.toHHMMSS = function () {    var sec_num = parseInt(this, 10); // don't forget the second param    var hours   = Math.floor(sec_num / 3600);    var minutes = Math.floor((sec_num - (hours * 3600)) / 60);    var seconds = sec_num - (hours * 3600) - (minutes * 60);    if (hours   < 10) {hours   = "0"+hours;}    if (minutes < 10) {minutes = "0"+minutes;}    if (seconds < 10) {seconds = "0"+seconds;}    return hours+':'+minutes+':'+seconds;}

You can use it now like:

alert("5678".toHHMMSS());

Working snippet:

String.prototype.toHHMMSS = function () {    var sec_num = parseInt(this, 10); // don't forget the second param    var hours   = Math.floor(sec_num / 3600);    var minutes = Math.floor((sec_num - (hours * 3600)) / 60);    var seconds = sec_num - (hours * 3600) - (minutes * 60);    if (hours   < 10) {hours   = "0"+hours;}    if (minutes < 10) {minutes = "0"+minutes;}    if (seconds < 10) {seconds = "0"+seconds;}    return hours +':'+ minutes +':'+ seconds;}console.log("5678".toHHMMSS());