[프로그래머스 Lv.1] 2016년

function solution(a, b) {
  const day = ['SUN', 'MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT'];
  return day[new Date(`2016/${a}/${b}`).getDay()];
}

// ----- 다른 방법 -----

function solution(a, b) {
  const month = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
  const week = ['THU', 'FRI', 'SAT', 'SUN', 'MON', 'TUE', 'WED'];

  let day = b;

  for (let i = 0; i < a - 1; i++) day += month[i];

  return week[day % 7];
}