块上的字符串有一个新方法:padStart

const str = '5';
str.padStart(2, '0'); // 05

下面是一个示例用例:用4行JavaScript编写YouTube持续时间

如果你是在处理视频长度，这个版本的公认答案会让它看起来更漂亮:

1:37:40(1小时/ 37分钟/ 40秒)

1:00(1分钟)

2:20(2分20秒)

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);

  var hourSeparator = ':';
  var minuteSeparator = ':';

  if(hours == 0){hours = '';hourSeparator = '';}
  if (minutes < 10 && hours != 0) {minutes = "0"+minutes;}
  if (seconds < 10) {seconds = "0"+seconds;}
  var time = hours+hourSeparator+minutes+minuteSeparator+seconds;
  return time;
}

主题的变奏。处理个位数秒的方式有点不同

seconds2time(0)  ->  "0s" 
seconds2time(59) -> "59s" 
seconds2time(60) -> "1:00" 
seconds2time(1000) -> "16:40" 
seconds2time(4000) -> "1:06:40"

function seconds2time (seconds) {
    var hours   = Math.floor(seconds / 3600);
    var minutes = Math.floor((seconds - (hours * 3600)) / 60);
    var seconds = seconds - (hours * 3600) - (minutes * 60);
    var time = "";

    if (hours != 0) {
      time = hours+":";
    }
    if (minutes != 0 || time !== "") {
      minutes = (minutes < 10 && time !== "") ? "0"+minutes : String(minutes);
      time += minutes+":";
    }
    if (time === "") {
      time = seconds+"s";
    }
    else {
      time += (seconds < 10) ? "0"+seconds : String(seconds);
    }
    return time;
}

你可以使用moment .js的moment-duration-format插件:

Var秒= 3820; Var duration =时刻。持续时间(秒,“秒”); Var format = duration.format("hh:mm:ss"); console.log(格式化);/ / 01:03:40 <！——Moment.js库——> .js库 < script src = " https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js " > < /脚本> <！——moment-duration-format插件——> < script src = " https://cdnjs.cloudflare.com/ajax/libs/moment-duration-format/1.3.0/moment-duration-format.min.js " > < /脚本>

看看这把小提琴

如果你知道你有多少秒，这就可以了。它还使用本机Date()对象。

function formattime(numberofseconds){    
    var zero = '0', hours, minutes, seconds, time;

    time = new Date(0, 0, 0, 0, 0, numberofseconds, 0);

    hh = time.getHours();
    mm = time.getMinutes();
    ss = time.getSeconds() 

    // Pad zero values to 00
    hh = (zero+hh).slice(-2);
    mm = (zero+mm).slice(-2);
    ss = (zero+ss).slice(-2);

    time = hh + ':' + mm + ':' + ss;
    return time; 
}

我喜欢Powtac的答案，但我想在angular.js中使用它，所以我用他的代码创建了一个过滤器。

.filter('HHMMSS', ['$filter', function ($filter) {
    return function (input, decimals) {
        var sec_num = parseInt(input, 10),
            decimal = parseFloat(input) - sec_num,
            hours   = Math.floor(sec_num / 3600),
            minutes = Math.floor((sec_num - (hours * 3600)) / 60),
            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;}
        var time    = hours+':'+minutes+':'+seconds;
        if (decimals > 0) {
            time += '.' + $filter('number')(decimal, decimals).substr(2);
        }
        return time;
    };
}])

它在功能上是相同的，除了我添加了一个可选的小数字段来显示小数秒。像使用其他过滤器一样使用它:

{{elapsedTime | HHMMSS}}显示:01:23:45

{{elapsedTime | HHMMSS: 3}}显示:01:23:45.678