用 Javascript 获取一周中的天数，一周从周日开始

Question

以下是用户给出的输入：

年 = 2011 年，月 = 3（三月），周 = 2

我想在 JavaScript 中获取 2011 年 3 月第 2 周的天数。

例如，周日 6 号、周一 7 号、周二 8 号、周三 9 号、周四 10 号、周五 11 号、周六 12 号

有什么想法吗？谢谢！

Answer 1

var year = 2011;
var month = 3;
var week = 2;

dateNumbersOfMonthOnWeek

var firstDateOfMonth = new Date(year, month - 1, 1); // Date: year-month-01

var firstDayOfMonth = firstDateOfMonth.getDay();     // 0 (Sun) to 6 (Sat)

var firstDateOfWeek = new Date(firstDateOfMonth);    // copy firstDateOfMonth

firstDateOfWeek.setDate(                             // move the Date object
    firstDateOfWeek.getDate() +                      // forward by the number of
    (firstDayOfMonth ? 7 - firstDayOfMonth : 0)      // days needed to go to
);                                                   // Sunday, if necessary

firstDateOfWeek.setDate(                             // move the Date object
    firstDateOfWeek.getDate() +                      // forward by the number of
    7 * (week - 1)                                   // weeks required (week - 1)
);

var dateNumbersOfMonthOnWeek = [];                   // output array of date #s
var datesOfMonthOnWeek = [];                         // output array of Dates

for (var i = 0; i < 7; i++) {                        // for seven days...

    dateNumbersOfMonthOnWeek.push(                   // push the date number on
        firstDateOfWeek.getDate());                  // the end of the array

    datesOfMonthOnWeek.push(                         // push the date object on
        new Date(+firstDateOfWeek));                 // the end of the array

    firstDateOfWeek.setDate(
        firstDateOfWeek.getDate() + 1);              // move to the next day

}

给定然后

• 将获得该周的日期数字。
• datesOfMonthOnWeek 将包含该周的日期对象。

虽然这对于这项工作来说似乎有点大材小用，但要使其在所有情况下都有效，例如当日期数字跨越到另一个月份时，需要做很多工作。不过，我确信它可以优化得不那么冗长。

Answer 2

我通常使用 Datejs 在 js 中进行日期操作。我会这样做：

var firstDayOfWeek = new Date(year,month-1,1).moveToDayOfWeek(0,-1).addWeeks(week-1);
var lastDayOfWeek = firstDayOfWeek.addDays(6);

Answer 3

假设该月的第一周是该月的第一周，则以下函数将返回给定年、月和周数的该周第一天的日期：

/* 
   Input year, month and week number from 1
   Returns first day in week (Sunday) where
   first week is the first with 1st of month in it
*/
function getFirstDayOfWeek(y, m, w) {
  var d = new Date(y, --m);
  d.setDate(--w * 7 - d.getDay() + 1);
  return d;
}

alert(getFirstDayOfWeek(2011,3, 2)); // Sun Mar 06 2011

获取其余天数，只需循环6次，每次在日期上加1，例如

function getWeekDates(y, m, w) {
  var d = getFirstDayOfWeek(y, m, w)
  var week = [new Date(d)];
  var i = 6;
  while (i--) {
    week.push(new Date(d.setDate(d.getDate() + 1)));
  }
  return week;
}

// Show week of dates
var week = getWeekDates(2011,3, 2);
for (var i=0, iLen=week.length; i<iLen; i++) {
  alert(week[i]);
}

Answer 4

对第一个对我有用的答案进行一些修改：

year = 2014;
week = 31;//week number is 31 for the example, could be 120.. it will just jump trough years
// get the date for the first day of the year               
var firstDateOfYear = new Date(year,0,1);
// set the date to the number of days for the number of weeks
firstDateOfYear.setDate(firstDateOfYear.getDate()+(7 * (week-1))); 
// get the number of the day in the week 0 (Sun) to 6 (Sat)
var counter = firstDateOfYear.getDay();

//make sunday the first day of the week
for(i=0;i<counter;i++){
    firstDateOfYear.setDate(firstDateOfYear.getDate()-1)
}

var firstDateOfWeek = new Date(firstDateOfYear);    // copy firstDateOfYear

var dateNumbersOfMonthOnWeek = [];                   // output array of date #s
var datesOfMonthOnWeek = [];                         // output array of Dates

for (var i = 0; i < 7; i++) {                        // for seven days...
    dateNumbersOfMonthOnWeek.push(                   // push the date number on
        firstDateOfWeek.getDate());                  // the end of the array

 datesOfMonthOnWeek.push(                         // push the date object on
     new Date(+firstDateOfWeek));                 // the end of the array

 firstDateOfWeek.setDate(
    firstDateOfWeek.getDate() + 1);              // move to the next day
}