【TypeScript】Get a list of dates and days of the week for the target year and month【TypeScript】

/**
 * 対象年月の日付一覧を取得
 * @param year
 * @param month
 * @returns 対象年月の日付一覧
 */
export const getAllDays = (year: number, month: number): Date[] => {
  const date = new Date(year, month, 1)
  const dates = []

  while (date.getMonth() === month) {
    dates.push(new Date(date))
    date.setDate(date.getDate() + 1)
  }

  return dates
}

/**
 * 対象日の曜日を取得
 * @param date
 * @returns 対象日の曜日
 */
export const getDayOfWeek = (date: Date): string => {
  const day = date.getDay()
  const weekItems = ['日', '月', '火', '水', '木', '金', '土']

  return weekItems[day]
}