根据周数获取某周的第一天和最后一天

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//根据周数获取周的范围
function getFirstAndLastDayOfWeek(weekNumber, year) {
  // 确保周数和年份是有效的
  if (weekNumber < 1 || weekNumber > 54 || isNaN(year)) {
    return "Invalid input";
  }

  // 获取指定年份的第一个星期的起始日期
  var firstWeekStartDate = new Date(year, 0, 4); // 1 月 4 日所在的星期
  var iW = firstWeekStartDate.getDay();

  // 计算指定周的起始日期
  var targetWeekStartDate = new Date(firstWeekStartDate);
  // 计算指定周的结束日期
  var targetWeekEndDate = new Date(targetWeekStartDate);
  
  //直接向前推6天
  if(iW == 0)
  {
      targetWeekStartDate.setDate(firstWeekStartDate.getDate() - 6);
  }
  //周四这天在开头或者中间
  else
  {
      targetWeekStartDate.setDate(firstWeekStartDate.getDate() - (iW - 1));
      targetWeekEndDate.setDate(firstWeekStartDate.getDate() + (7 - iW));
  }
  
  targetWeekStartDate.setDate(targetWeekStartDate.getDate() + (weekNumber - 1) * 7);
  targetWeekEndDate.setDate(targetWeekEndDate.getDate() + (weekNumber - 1) * 7);

  return {
    firstDay: targetWeekStartDate.toDateString(),
    lastDay: targetWeekEndDate.toDateString()
  };
}