```

//date: yyyy[sep]MM[sep]dd

function getNextMonthDay(date, monthNum, sep) {

var dateArr = date.split(sep);

    var year = dateArr[0]; //获取当前日期的年份

    var month = dateArr[1]; //获取当前日期的月份

    var day = dateArr[2]; //获取当前日期的日

    var year2 = year;

    var month2 =parseInt(month) +parseInt(monthNum);

    if (month2 >12) {

year2 =parseInt(year2) +parseInt((parseInt(month2) /12 ==0 ?1 :parseInt(month2) /12));

        month2 =parseInt(month2) %12;

    }

var days2 =new Date(year2, month2, 0);

    days2 = days2.getDate();

    if (day < days2) {

days2 = day;

    }

if (month2 <10) {

month2 ='0' + month2;

    }

var t2 = year2 + sep + month2 + sep + days2;

    return t2;

}

```