JS- Confirm Box

<!DOCTYPE html>
<html>

  <head>
    <script type="text/javascript">
      var check;
      function msg()
      {
        check=confirm("Do you want to exit?")
        document.write(check);
      }
    </script>
  </head>

  <body>
    <button type="button" onClick="msg()">Click</button>
  </body>

</html>