Lý thuyết: 1 mili giây = 0.001 giây -> 1,000 mili giây = 1 giây

Hàm 1: Chuyển từ 1,000 mili giây -> 00:00:01

function msToTime(duration) {
  var milliseconds = Math.floor((duration % 1000) / 100),
    seconds = Math.floor((duration / 1000) % 60),
    minutes = Math.floor((duration / (1000 * 60)) % 60),
    hours = Math.floor((duration / (1000 * 60 * 60)) % 24);

  hours = (hours < 10) ? "0" + hours : hours;
  minutes = (minutes < 10) ? "0" + minutes : minutes;
  seconds = (seconds < 10) ? "0" + seconds : seconds;

  return hours + ":" + minutes + ":" + seconds + "." + milliseconds;
}
console.log(msToTime(300000))

Hàm 2: Hàm chuyển từ 1,000 mili giây -> 00:00:01

function msToTime(ms) {
  let seconds = (ms / 1000).toFixed(1);
  let minutes = (ms / (1000 * 60)).toFixed(1);
  let hours = (ms / (1000 * 60 * 60)).toFixed(1);
  let days = (ms / (1000 * 60 * 60 * 24)).toFixed(1);
  if (seconds < 60) return seconds + " Sec";
  else if (minutes < 60) return minutes + " Min";
  else if (hours < 24) return hours + " Hrs";
  else return days + " Days"
}

console.log(msToTime(1000))
console.log(msToTime(10000))
console.log(msToTime(300000))
console.log(msToTime(3600000))
console.log(msToTime(86400000))