在Javascript中获取一周中的天数，一周从周日开始

Question

下面是用户给出的输入:

年= 2011，月= 3(三月)，周= 2

我想在JavaScript中得到2011年3月第2周的天数。

。星期日6日，星期一7日，星期二8日，星期三9日，星期四10日，星期五11日，星期六12日

任何想法?谢谢!

Answer 1

给定

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

和

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
}

然后

• dateNumbersOfMonthOnWeek将显示该星期的日期。
• datesOfMonthOnWeek将有该星期的日期对象。

虽然这看起来有点小题大做，但这是所有情况下都需要的，比如当日期数字交叉到另一个月时。我确信它可以被优化得不那么冗长。

Answer 2

我通常在js中使用Datejs进行日期操作。我想这样做:

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天，那么下面的函数将返回给定年、月和周号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

要得到剩下的天数，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

对第一个答案的一点修改:

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
}