利用函数判断闰年

<script>
    function run(year) {
      let a = false;
      if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
        a = true;
      }
      return a;
    }
    console.log(run(2000));
    console.log(run(2021));
  </script>