asp 월별 마지막일 추출

// # 월별 일자수 추출 ##################################################
function getLastDay(year, mon) {
var last_day = 31;

switch(mon) {
case(1): last_day=31; break;
case(2):
// 윤년 확인
if(((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) {
last_day=29;
}
else{
last_day=28;
}
break;
case(3): last_day=31; break;
case(4): last_day=30; break;
case(5): last_day=31; break;
case(6): last_day=30; break;
case(7): last_day=31; break;
case(8): last_day=31; break;
case(9): last_day=30; break;
case(10): last_day=31; break;
case(11): last_day=30; break;
case(12): last_day=31; break;
default: last_day=31; break;
}

return last_day;
}