Resolved: Formatting custom date timestamp in Javascript

const formatTimeFromSeconds = (seconds) => {
  dateObj = new Date(seconds * 1000);
  hours = dateObj.getUTCHours();
  minutes = dateObj.getUTCMinutes();
  seconds = dateObj.getSeconds();
  milliseconds = dateObj.getMilliseconds();

  timeString =
    hours.toString().padStart(2, "0") +
    ":" +
    minutes.toString().padStart(2, "0") +
    ":" +
    seconds.toString().padStart(2, "0") +
    "," +
    milliseconds.toString().padStart(2, "0");

  return timeString;
};

const dateToSeconds = (time) => {
  try {
    const times = time.split(":")
    const secondDelimit = times[2].split(".")
    const secondsConversion = parseInt(secondDelimit[0])
    const hoursToSeconds = parseInt(times[0]) * 60 * 60
    const minutesToSeconds = parseInt(times[1]) * 60 

    const totalSeconds = minutesToSeconds + hoursToSeconds + secondsConversion
    return `${totalSeconds}.${secondDelimit[1]}`
  } catch (err) {
    console.error(err)
  }
}

const formatTimeFromSeconds = (seconds) => {
    const date = new Date(seconds*1000);
    return date.toISOString().match(/^.*T(.*)\d{1}Z$/)[1].replace(".",",");
}