HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>Password length</title>
</head>
<body>
  <h1>Password validation</h1>
  <pre id="out"></pre>
  <script>
    function validatePassword(password) {
      if (password.length < 8) return "Password must be at least 8 characters.";
      if (password.length > 128) return "Password is too long.";
      return "Password accepted.";
    }
    document.getElementById("out").textContent =
      validatePassword("short") + "\n" +
      validatePassword("mypassword");
  </script>
</body>
</html>

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JavaScript String length — password validation (Try It)