평균 점수 구하기

const grade = (arr) => {
  const average =
    arr.reduce((sum, currValue) => sum + currValue, 0) / arr.length;
  if (average >= 90) return "A";
  if (average >= 80) return "B";
  if (average >= 70) return "C";
  if (average >= 50) return "D";
  return "F";
};
function solution(scores) {
  const item = scores.map((_, arrIndex) => {
    let group = scores.map((_, numIndex) => scores[numIndex][arrIndex]);
    const personNum = group[arrIndex];
    if (
      personNum === Math.max.apply(null, group) ||
      personNum === Math.min.apply(null, group)
    ) {
      group.filter((num) => num === personNum).length === 1 &&
        group.splice(arrIndex, 1);
    }
    return grade(group);
  });
  return item.join("");
}