JS Date processing Function--judge leap year, get total number of days in the month, add month

1. Determine if a leap year

function Isleapyear (eDate) {    var year = edate.getfullyear ();     return (((0 = = year% 4) && (0! = (year% 100))) | | (0 = = year%));}

2. Get the total number of days in a month

function Getdaysinmonth (eDate) {    var daysinmonth = [31,28,31,30,31,30,31,31,30,31,30,31];    daysinmonth[1] = Isleapyear (eDate)? 29:28;     return Daysinmonth[edate.getmonth ()];}

3. Add a few months to the date (if the date you get does not have this day, it will automatically become the last day of the month)

function addmonth (eDate, duration) {    var month = Edate.getmonth () + parseint (duration);     var day = edate.getdate ();      Edate.setdate (1);      Edate.setmonth (month);     var daysinmonth = getdaysinmonth (eDate);     if (Day > daysinmonth) {        = daysinmonth;    }    Edate.setdate (day);     return eDate;}

4. Date Modified

function changeexpirydate (expdate, Duration, durationtype) {    if(Durationtype = = 2) {//Day         expdate.setdate (expdate.getdate () +parseint (duration));    } Else if (Durationtype = = 3) {//Week        expdate.setdate (Expdate.getdate () +parseint (duration*7));    } Else if (Durationtype = = 4) {//Month        expdate = addmonth (Expdate.gettime (), duration);}    }

JS Date processing function--judging leap years, getting the total number of days in the month, adding a month