如何显示31-03- year的结束日期(取决于start_date)？

function getEndDate(start_date) {
  var parts = start_date.split('-');
  var day = parseInt(parts[0]);
  var month = parseInt(parts[1]);
  var year = parseInt(parts[2]);

  var end_day;
  if (month === 2) {
    if ((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0) {
      end_day = 29;
    } else {
      end_day = 28;
    }
  } else if (month === 4 || month === 6 || month === 9 || month === 11) {
    end_day = 30;
  } else {
    end_day = 31;
  }

  var end_date = end_day + '-' + parts[1] + '-' + parts[2];
  return end_date;
}

var start_date = '01-03-2022';
var end_date = getEndDate(start_date);
console.log(end_date);