pub.solar/scripts/hakken-dates.js

const skippedMonths = [
  { m: 8, y: 2022 },
  { m: 12, y: 2022 },
  { m: 4, y: 2023 },
  { m: 12, y: 2023 },
];

const i18n = {
  en: {
    comingDates: 'The following dates are scheduled:',
    friday: 'friday',
    sunday: 'sunday',
    until: 'until',
    months: [
      'Jan.',
      'Feb.',
      'Mar.',
      'Apr.',
      'May',
      'Jun.',
      'Jul.',
      'Aug.',
      'Sep.',
      'Oct.',
      'Nov.',
      'Dec.',
    ],
  },
  de: {
    comingDates: 'Folgende Termine stehen an:',
    friday: 'Freitag',
    sunday: 'Sonntag',
    until: 'bis',
    months: [
      'Jan.',
      'Feb.',
      'Mär.',
      'Apr.',
      'Mai',
      'Jun.',
      'Jul.',
      'Aug.',
      'Sep.',
      'Okt.',
      'Nov.',
      'Dez.',
    ],
  },
};

const datesLists = {
  en: document.getElementById('dates-list-en'),
  de: document.getElementById('dates-list-de'),
};

const day = 24 * 60 * 60 * 1000;
const week = 7 * day;
const endOfWeekend = 2 * day;
const start = new Date();
const hakkens = [];
// We'll be looking about half a year into the future
for (let i = 0; i < 185; i++) {
  const dateToTry = new Date(start.valueOf() + (i * day));
  if (dateToTry.getDay() !== 5) {
    continue;
  }

  const oneWeekLater = new Date(dateToTry.valueOf() + week);
  if (dateToTry.getMonth() === oneWeekLater.getMonth()) {
    continue;
  }

  const m = dateToTry.getMonth() + 1;
  const y = dateToTry.getFullYear();
  if (skippedMonths.find((s) => s.m === m && s.y === y)) {
    continue;
  }
  hakkens.push(dateToTry);
}

// Helper function to add leading zeros to dates
const d = (num) => ('0' + num).slice(-2);

const writeText = (lang) => {
  const p = document.createElement('p');
  p.innerHTML = i18n[lang].comingDates;
  datesLists[lang].appendChild(p);
}

const writeDateList = (lang) => {
  const ul = document.createElement('ul');
  hakkens.forEach(hakken => {
    hakkend = new Date(hakken.valueOf() + endOfWeekend);
    const showFirstMonth = hakken.getMonth() !== hakkend.getMonth();
    const li = document.createElement('li');
    li.innerHTML = `
      ${i18n[lang].friday} ${d(hakken.getDate())}. ${showFirstMonth ? i18n[lang].months[hakken.getMonth()] : ''}
      ${i18n[lang].until}
      ${d(hakkend.getDate())}. ${i18n[lang].months[hakkend.getMonth()]}
    `;
    ul.appendChild(li);
  });
  datesLists[lang].appendChild(ul);
}

writeText('de');
writeText('en');
writeDateList('de');
writeDateList('en');