SOURCE

function addMonth(date, monthNum)
 {
  var dateArr = date.split('-');
  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 days = new Date(year, month, 0);
  days = days.getDate(); //获取当前日期中的月的天数
  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 day2 = day;
  var days2 = new Date(year2, month2, 0);
  days2 = days2.getDate();
  if (day2 > days2) {
   day2 = days2;
  }
  if (month2 < 10) {
   month2 = '0' + month2;
  }
  var t2 = year2 + '-' + month2 + '-' + day2;
  return t2;
}

console.log(addMonth('2022-07-15',5));