JSFiddle - React, Tailwind, and code Playground

HTML

<script>
function myGender() {
  /* gender=document.querySelector('input[name="gender"]:checked').value; */
  if (document.querySelector('input[name="gender"]:checked').value==null) {
    document.getElementById('demo').innerHTML = "Please select your gender";
  } else {
    document.getElementById('demo').innerHTML = document.querySelector('input[name="gender"]:checked').value;
  }
}

</script>
<body>
      <label for="gender"> Gender: </label> <br>
      <input type="radio" name="gender" value="man"> man<br>
      <input type="radio" name="gender" value="woman" >woman<br>
      <input type="radio" name="gender" value="Other" >Other<br>
      <button onclick="myGender()">What am I?</button>
     <p id="demo"></p>
</body>