JavaScript calculator: JavaScript calculates the current date is the year and the first weeks of the month

Calculates the number of weeks of the current date in this year
Date.prototype.getWeekOfYear = function (Weekstart) {//Weekstart: Weekly start in week: Sunday: 0, Monday: 1, Tuesday: 2 ..., default to Sunday
Weekstart = (weekstart 0)-0;
if (isNaN (Weekstart) weekstart > 6)
Weekstart = 0;
var year = This.getfullyear ();
var firstday = new Date (year, 0, 1);
var firstweekdays = 7-firstday.getday () + Weekstart;
var dayofyear = ((New Date (year, This.getmonth (), This.getdate ())-FirstDay)/(24 * 3600 * 1000)) + 1;
Return Math.ceil ((dayofyear-firstweekdays)/7) + 1;
}
Calculates the number of weeks of the current date in this month
Date.prototype.getWeekOfMonth = function (Weekstart) {
Weekstart = (weekstart 0)-0;
if (isNaN (Weekstart) weekstart > 6)
Weekstart = 0;
var DayOfWeek = This.getday ();
var day = This.getdate ();
Return Math.ceil ((day-dayofweek-1)/7) + ((DayOfWeek >= weekstart)? 1:0);
}
Use
var date = new Date (2011, 11, 31); Note: The value range of JS in the month is 0~11
var weekofyear = Date.getweekofyear (); The current date is the first weeks of the year
var weekofmonth = Date.getweekofmonth (); The current date is the first few weeks of this month
2011 is a couple of weeks.
(New Date (a)). Getweekofyear ();
2011 A few weeks in January
(New Date (0)). Getweekofmonth ();
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