Date Formatting in JavaScript

dateFormatter.js

const months = [
  'January',
  'February',
  'March',
  'April',
  'May',
  'June',
  'July',
  'August',
  'September',
  'October',
  'November',
  'December'
];

const days = [
  'Monday',
  'Tuesday',
  'Wednesday',
  'Thursday',
  'Friday',
  'Saturday',
  'Sunday'
];

export const formatDate = (date, format) => {
  const secondFormats = ['s', 'ss'].sort((a, b) => b.length - a.length);
  const minuteFormats = ['m', 'mm'].sort((a, b) => b.length - a.length);
  const hourFormats = ['H', 'HH'].sort((a, b) => b.length - a.length);
  const dayFormats = ['dd', 'ddd', 'dddd'].sort((a, b) => b.length - a.length);
  const monthFormats = ['MM', 'MMM', 'MMMM'].sort((a, b) => b.length - a.length);
  const yearFormats = ['yyyy'].sort((a, b) => b.length - a.length);

  secondFormats.forEach(sf => {
    const regex = new RegExp(sf, 'g');

    switch (sf) {
      case 'ss':
        let seconds = date.getSeconds().toString();
        let length = seconds.length;

        if (!--length) {
          seconds = `0${seconds}`;
        }

        format = format.replace(regex, seconds);
        break;
      case 's':
        format = format.replace(regex, date.getSeconds().toString());
        break;
      default:
        return;
    }
  });

  minuteFormats.forEach(mf => {
    const regex = new RegExp(mf, 'g');

    switch (mf) {
      case 'mm':
        let minutes = date.getMinutes().toString();
        let length = minutes.length;

        if (!--length) {
          minutes = `0${minutes}`;
        }

        format = format.replace(regex, minutes);
        break;
      case 'm':
        format = format.replace(regex, date.getMinutes().toString());
        break;
      default:
        return;
    }
  });

  hourFormats.forEach(hf => {
    const regex = new RegExp(hf, 'g');

    switch (hf) {
      case 'HH':
        let hours = date.getHours().toString();
        let length = hours.length;

        if (!--length) {
          hours = `0${hours}`;
        }

        format = format.replace(regex, hours);
        break;
      case 'H':
        format = format.replace(regex, date.getHours().toString());
        break;
      default:
        return;
    }
  });

  dayFormats.forEach(df => {
    const regex = new RegExp(df, 'g');

    switch (df) {
      case 'dddd':
        format = format.replace(regex, days[date.getDay()]);
        break;
      case 'ddd':
        format = format.replace(regex, days[date.getDay()].substr(0, df.length));
        break;
      case 'dd':
        format = format.replace(regex, date.getDate().toString());
        break;
      default:
        return;
    }
  });

  monthFormats.forEach(mf => {
    const regex = new RegExp(mf, 'g');

    switch (mf) {
      case 'MMMM':
        format = format.replace(regex, months[date.getMonth()]);
        break;
      case 'MMM':
        format = format.replace(regex, months[date.getMonth()].substr(0, mf.length));
        break;
      case 'MM':
        let month = date.getMonth();

        format = format.replace(regex, (++month).toString());
        break;
      default:
        return;
    }
  });

  yearFormats.forEach(yf => {
    const regex = new RegExp(yf, 'g');

    switch (yf) {
      case 'yyyy':
        format = format.replace(regex, date.getFullYear().toString());
        break;
      default:
        return;
    }
  });

  return format;
};