@jk-core/components/src/Calendar/utils/getWeeksInMonth.ts

components for jk

const getWeeksInMonth = (viewDate:Date) => {
  const startOfMonth = new Date(viewDate.getFullYear(), viewDate.getMonth(), 1);
  const endOfMonth = new Date(viewDate.getFullYear(), viewDate.getMonth() + 1, 0);
  const weeks = [];
  let currentWeek = [];

  const startDayOfWeek = startOfMonth.getDay();
  if (startDayOfWeek !== 0) {
    const prevMonthEnd = new Date(startOfMonth);
    prevMonthEnd.setDate(0);
    for (let i = startDayOfWeek - 1; i >= 0; i -= 1) {
      const prevDate = new Date(prevMonthEnd);
      prevDate.setDate(prevMonthEnd.getDate() - i);
      currentWeek.push({ thisMonth: 'before', date: prevDate });
    }
  }

  const currentDate = new Date(startOfMonth);

  while (currentDate <= endOfMonth) {
    currentWeek.push({ thisMonth: 'this', date: new Date(currentDate) });
    if (currentDate.getDay() === 6) {
      weeks.push(currentWeek);
      currentWeek = [];
    }
    currentDate.setDate(currentDate.getDate() + 1);
  }

  const endDayOfWeek = endOfMonth.getDay();
  if (endDayOfWeek !== 6) {
    for (let i = 1; i <= 6 - endDayOfWeek; i += 1) {
      const nextDate = new Date(endOfMonth);
      nextDate.setDate(endOfMonth.getDate() + i);
      currentWeek.push({ thisMonth: 'after', date: nextDate });
    }
  }

  if (currentWeek.length > 0) {
    weeks.push(currentWeek);
  }

  return weeks;
};

export default getWeeksInMonth;