Add `n` month to the current date, using the last day of the target month rather than rolling over to following month.

addMonth.js

/**
 * Add `n` months to the current date.
 * If the target month as fewer days than the source month
 * (i.e. 28 or 29 vs 30, or 30 vs 31) then go to the last
 * day of the month.
 */
function addMonth(d, n) {
  let d1 = d.getUTCDate();
  let m1 = d.getUTCMonth();
  
  d.setUTCMonth(m1 + n);
  let m2 = d.getUTCMonth();
  
  if (m1 + n !== m2) {
    // Go to the last day of the previous month
    d.setUTCDate(0);
  }
}

var d = new Date('2022-01-30T23:00:00Z');
addMonth(d, 1);
// 2022-02-28T23:00:00Z

var d = new Date('2022-01-30T23:00:00Z');
addMonth(d, 2);
// 2022-03-30T23:00:00Z
addMonth(d, 11);
// 2023-01-28T23:00:00Z