HTML Code

<!DOCTYPE html>
<html lang=en>
<head>
  <meta charset=utf-8>
  <title>Leap year — single</title>
</head>
<body>
  <h1>Leap year check</h1>
  <p>Edit <code>year</code>, then <strong>Run</strong>.</p>
  <pre id=out></pre>
  <script>
    (function () {
      function isLeapYear(year) {
        return (
          (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0
        );
      }
      var year = 2024;
      document.getElementById("out").textContent = isLeapYear(year)
        ? year + " is a leap year."
        : year + " is not a leap year.";
    })();
  </script>
</body>
</html>

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JavaScript Leap Year — Single year (Try It)