JS gets the last days of the month, the maximum days and the number of days of the week _javascript skills

Source: Internet
Author: User
Tags getdate

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JS gets one months maximum days

JS inside of the new date ("Xxxx/xx/xx") the date of the construction method has a beauty,
When you pass in the "xxxx/xx/0" (number No. 0), the date is the "XX" month the first one months of the last day ("XX" month's maximum value is 69, digression),
When you pass in the "XXXX/XX/1" (number 1th), the date is "XX" month after the first day of one months (oneself understand)
If you pass in "1999/13/0", you will get "1998/12/31". And the biggest advantage is that when you pass in "xxxx/3/0", will get XXXX year February of the last day, it will automatically determine whether it is a leap year to return 28 or 29, do not judge yourself,
So, we want to choose how many days the choice of year, only need

```var temp=new Date ("Select year/Select Month +1/0");
return temp.getdate ()//Maximum days

```

Check, you can also use this method.

The following is a getdaysinmonth (year, Month) method written using JS to obtain the number of days of a certain month:

```function Getdaysinmonth (year,month) {
month = parseint (month,10) +1;
var temp = new Date (year+ "/" +month+ "/0");
return Temp.getdate ();
}

```

JS to get the day of the year is the first few weeks

```/** * To determine whether the year is run year * * @param {Number} years/function Isleapyear {return (400 = 0) | |
(Year% 4 = 0 && Year% 100!= 0); /** * Get a January number of days in a year * * @param {numbers} years * @param {numbers} month/function getmonthdays (yearly, month) {RET urn [to, null, 31][month, M, M, M, M] | |
(Isleapyear (year) 29:28); /** * Get the day of the year is the first weeks * @param {number} y * @param {number} m * @param {number} D * @returns {Number} * */function gets WeekNumber (Y, M, d) {var now = new Date (y, m-1, D), year = Now.getfullyear (), month = Now.getmonth (), Day
s = now.getdate ();
That day is the number of days of that year for (var i = 0; i < month i++) {day = Getmonthdays (year, i); The first day of the year is the week. var yearfirstday = new Date (years, 0, 1). Getday () | |
7;
var week = null;
if (Yearfirstday = = 1) {week = Math.ceil (days/yearfirstday);
else {days = (7-yearfirstday + 1);
Week = Math.ceil (DAYS/7) + 1;
Return week;

}```

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