Delete occurrences of an element if it occurs more than n times

function deleteNth(arr,n){
  let countNumber = {};
  for (let i=0; i<arr.length; i++){
    let a = arr[i];
    if (countNumber[a] != undefined) {
      ++countNumber[a];
    } else {
      countNumber[a] = 1;
    };
  };
  
  for (let key in countNumber) {
    if(countNumber[key]>n) {
      for (let i=0; i<(countNumber[key]-n); i++){
        console.log(key);
        arr.splice(arr.lastIndexOf(Number(key)), 1);
      }
    }
  }

  return arr;
};