Generate filename with date

genFileDateName.js

/**
 * Return a timestamp with the format "m-d-yy"
 * @type {Date}
 */

function timeStamp() {
  // Create a date object with the current time
  let now = new Date();

  // Create an array with the current month, day and time
  let date = [now.getMonth() + 1, now.getDate(), now.getFullYear()];

  // Return the formatted string
  return date.join("-");
}

/**
 * Return a timestamp with the format "m-d-yy_hh:MM:ss"
 * @type {Date}
 */

function timeStampWithTime() {
  // Create a date object with the current time
  let now = new Date();

  // Create an array with the current month, day and time
  let date = [now.getMonth() + 1, now.getDate(), now.getFullYear()];

  // Create an array with the current hour, minute and second
  let time = [now.getHours(), now.getMinutes(), now.getSeconds()];
  time = time.map(e => {
    if (e < 10) {
      return (e + "").padStart(2, "0");
    } else {
      return e;
    }
  });
  // Return the formatted string
  return date.join("-") + "_" + time.join("-");
}

function timeStampPretty() {
  // Create a date object with the current time
  let now = new Date();

  /**
   * SUFFIX GETTING
   * @type {{month: string, year: string, day: string}}
   */

  let options = { day: "numeric", year: "numeric", month: "long" };
  let sfx = ["th", "st", "nd", "rd"];
  let val = now.getDate() % 100;

  let sffx = sfx[(val - 20) % 10] || sfx[val] || sfx[0];
  let dddd = now.toLocaleDateString("en-US", options); // Saturday, September 17, 2016
  let partsz = dddd.split(",");
  let month = partsz[0].split(" ")[0];
  // " " +
  // partsz[0].split(" ")[1] +
  // sffx +
  // "," +
  // partsz[1];

  // Create an array with the current month, day and time
  let date = [month, now.getDate() + sffx, now.getFullYear()];

  // Create an array with the current hour, minute and second
  let time = [now.getHours(), now.getMinutes(), now.getSeconds()];
  time = time.map(e => {
    if (e < 10) {
      return (e + "").padStart(2, "0");
    } else {
      return e;
    }
  });

  // Return the formatted string
  return date.join(" ") + " " + time.join(":");
}

timeStampPretty(); //?

function twoDigitPad(num) {
  return num < 10 ? "0" + num : num;
}

function timeStampFormat(patternStr = "M/d/yyyy", date = new Date()) {
  let monthNames = [
    "January",
    "February",
    "March",
    "April",
    "May",
    "June",
    "July",
    "August",
    "September",
    "October",
    "November",
    "December"
  ];
  let dayOfWeekNames = [
    "Sunday",
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday",
    "Saturday"
  ];

  if (!patternStr) {
    patternStr = "M/d/yyyy";
  }
  let day = date.getDate(),
    month = date.getMonth(),
    year = date.getFullYear(),
    hour = date.getHours(),
    minute = date.getMinutes(),
    second = date.getSeconds(),
    h = hour % 12,
    hh = twoDigitPad(h),
    HH = twoDigitPad(hour),
    mm = twoDigitPad(minute),
    suffix = (() => {
      let sfx = ["th", "st", "nd", "rd"];
      let val = date.getDate() % 100;

      let sffx = sfx[(val - 20) % 10] || sfx[val] || sfx[0];
      return sffx;
    })();
  (ss = twoDigitPad(second)),
    (aaa = hour < 12 ? "AM" : "PM"),
    (EEEE = dayOfWeekNames[date.getDay()]),
    (EEE = EEEE.substr(0, 3)),
    (D = twoDigitPad(day)),
    (M = month + 1),
    (MM = twoDigitPad(M)),
    (MMMM = monthNames[month]),
    (MMM = MMMM.substr(0, 3)),
    (yyyy = year + ""),
    (yy = yyyy.substr(2, 2));
  // checks to see if month name will be used
  patternStr = patternStr
    .replace("hh", hh)
    .replace("h", h)
    .replace("HH", HH)
    .replace("H", hour)
    .replace("mm", mm)
    .replace("m", minute)
    .replace("ss", ss)
    .replace("s", second)
    .replace("Z", suffix)
    .replace("D", D)
    .replace("d", day)

    .replace("EEEE", EEEE)
    .replace("EEE", EEE)
    .replace("yyyy", yyyy)
    .replace("yy", yy)
    .replace("aaa", aaa);
  if (patternStr.indexOf("MMM") > -1) {
    patternStr = patternStr.replace("MMMM", MMMM).replace("MMM", MMM);
  } else {
    patternStr = patternStr.replace("MM", MM).replace("M", M);
  }
  return patternStr;
}

console.log(timeStampFormat());
console.log(timeStampFormat("DZ-MMM-yyyy")); //OP's request
console.log(timeStampFormat("dZ-MMM-yyyy")); //OP's request
console.log(timeStampFormat("EEEE, MMMM Z, yyyy HH:mm:ss aaa"));
console.log(timeStampFormat("EEE, MMM dZ, yyyy HH:mm"));
console.log(timeStampFormat("yyyy-MM-dZ HH:mm:ss"));
console.log(timeStampFormat("M/d/yyyy HH:mm aaa"));