write a code for aurthonage in html and javascript with database connectivity

<form>
  <input type="text" name="firstname" placeholder="First Name">
  <input type="text" name="lastname" placeholder="Last Name">
  <input type="password" name="password" placeholder="Password">
  <input type="text" name="email" placeholder="Email">
  <input type="submit" value="Register">
</form>
<script type="text/javascript">
  $(document).ready(function(){
  $("form").submit(function(e){
    e.preventDefault();
    $.ajax({
      url:"register.php",
      method: "POST",
      data:$("form").serialize(),
      dataType:"text",
      success: function(strmessage){
        $("#message").text(strmessage)
      }
    })
  })
})
</script>