var  timeInSec = "661"; //even it can be string

String.prototype.toHHMMSS = function () { 
   /* extend the String by using prototypical inheritance */
    var seconds = parseInt(this, 10); // don't forget the second param
    var hours   = Math.floor(seconds / 3600);
    var minutes = Math.floor((seconds - (hours * 3600)) / 60);
    seconds = seconds - (hours * 3600) - (minutes * 60);

    if (hours   < 10) {hours   = "0"+hours;}
    if (minutes < 10) {minutes = "0"+minutes;}
    if (seconds < 10) {seconds = "0"+seconds;}
    var time    = hours+':'+minutes+':'+seconds;
    return time;
}

alert("5678".toHHMMSS());   // "01:34:38"
console.log(timeInSec.toHHMMSS());   //"00:11:01"

我们可以把这个函数写得更短更清晰，但这会降低可读性，所以我们要把它写得尽可能简单，尽可能稳定。

或者你可以在这里检查一下:

试试这个:

function toTimeString(seconds) {
  return (new Date(seconds * 1000)).toUTCString().match(/(\d\d:\d\d:\d\d)/)[0];
}

这里没有一个答案满足我的要求，因为我想能够处理

大量的秒(天)，以及 负数

尽管OP不要求这些，但是覆盖边缘情况是一个很好的实践，特别是当它不需要花费太多精力时。

很明显，当他说秒的时候，OP的意思是秒的数量。为什么要把函数固定在字符串上?

function secondsToTimeSpan(seconds) {
    const value = Math.abs(seconds);
    const days = Math.floor(value / 1440);
    const hours = Math.floor((value - (days * 1440)) / 3600);
    const min = Math.floor((value - (days * 1440) - (hours * 3600)) / 60);
    const sec = value - (days * 1440) - (hours * 3600) - (min * 60);
    return `${seconds < 0 ? '-':''}${days > 0 ? days + '.':''}${hours < 10 ? '0' + hours:hours}:${min < 10 ? '0' + min:min}:${sec < 10 ? '0' + sec:sec}`
}
secondsToTimeSpan(0);       // => 00:00:00
secondsToTimeSpan(1);       // => 00:00:01
secondsToTimeSpan(1440);    // => 1.00:00:00
secondsToTimeSpan(-1440);   // => -1.00:00:00
secondsToTimeSpan(-1);      // => -00:00:01

这里有一个转换时间的简单函数，可能会有帮助

function formatSeconds(seconds) {
    var date = new Date(1970,0,1);
    date.setSeconds(seconds);
    return date.toTimeString().replace(/.*(\d{2}:\d{2}:\d{2}).*/, "$1");
}

这个函数应该这样做:

var convertTime = function (input, separator) {
    var pad = function(input) {return input < 10 ? "0" + input : input;};
    return [
        pad(Math.floor(input / 3600)),
        pad(Math.floor(input % 3600 / 60)),
        pad(Math.floor(input % 60)),
    ].join(typeof separator !== 'undefined' ?  separator : ':' );
}

在不传递分隔符的情况下，它使用:作为(默认)分隔符:

time = convertTime(13551.9941351); // --> OUTPUT = 03:45:51

如果你想使用-作为分隔符，只需将其作为第二个参数传递:

time = convertTime(1126.5135155, '-'); // --> OUTPUT = 00-18-46

看看这小提琴。

var time1 = date1.getTime();
var time2 = date2.getTime();
var totalMilisec = time2 - time1;

alert(DateFormat('hh:mm:ss',new Date(totalMilisec)))

 /* ----------------------------------------------------------
 *  Field        | Full Form          | Short Form
 *  -------------|--------------------|-----------------------
 *  Year         | yyyy (4 digits)    | yy (2 digits)
 *  Month        | MMM (abbr.)        | MM (2 digits)
                 | NNN (name)         |
 *  Day of Month | dd (2 digits)      | 
 *  Day of Week  | EE (name)          | E (abbr)
 *  Hour (1-12)  | hh (2 digits)      | 
 *  Minute       | mm (2 digits)      | 
 *  Second       | ss (2 digits)      | 
 *  ----------------------------------------------------------
 */
function DateFormat(formatString,date){
    if (typeof date=='undefined'){
    var DateToFormat=new Date();
    }
    else{
        var DateToFormat=date;
    }
    var DAY         = DateToFormat.getDate();
    var DAYidx      = DateToFormat.getDay();
    var MONTH       = DateToFormat.getMonth()+1;
    var MONTHidx    = DateToFormat.getMonth();
    var YEAR        = DateToFormat.getYear();
    var FULL_YEAR   = DateToFormat.getFullYear();
    var HOUR        = DateToFormat.getHours();
    var MINUTES     = DateToFormat.getMinutes();
    var SECONDS     = DateToFormat.getSeconds();

    var arrMonths = new Array("January","February","March","April","May","June","July","August","September","October","November","December");
    var arrDay=new Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday');
    var strMONTH;
    var strDAY;
    var strHOUR;
    var strMINUTES;
    var strSECONDS;
    var Separator;

    if(parseInt(MONTH)< 10 && MONTH.toString().length < 2)
        strMONTH = "0" + MONTH;
    else
        strMONTH=MONTH;
    if(parseInt(DAY)< 10 && DAY.toString().length < 2)
        strDAY = "0" + DAY;
    else
        strDAY=DAY;
    if(parseInt(HOUR)< 10 && HOUR.toString().length < 2)
        strHOUR = "0" + HOUR;
    else
        strHOUR=HOUR;
    if(parseInt(MINUTES)< 10 && MINUTES.toString().length < 2)
        strMINUTES = "0" + MINUTES;
    else
        strMINUTES=MINUTES;
    if(parseInt(SECONDS)< 10 && SECONDS.toString().length < 2)
        strSECONDS = "0" + SECONDS;
    else
        strSECONDS=SECONDS;

    switch (formatString){
        case "hh:mm:ss":
            return strHOUR + ':' + strMINUTES + ':' + strSECONDS;
        break;
        //More cases to meet your requirements.
    }
}