First JavaScript

<!DOCTYPE html>
<html lang="en">
<head>
  
  <script language="javascript" type="application/javascript">

     document.write ("Hello Friends<br><br>");

     function giveMessage() {
          alert("Your payment has been sent successfully!");
}

  </script>

 </head>

<body>

 <input type="button" onclick="giveMessage()" value="New Message!"/>

</body>
</html>