HubSpot Form Submission Callback.js

<script charset="utf-8" type="text/javascript" src="//js.hsforms.net/forms/v2.js"></script>
<script>
  hbspt.forms.create({
    region: "na1",
    portalId: "XXXXXX",
    formId: "XXXXX-XXXXXX-XXXXX-CCCC",
    onFormSubmit: function($form){
       setTimeout(function () {
          var firstName = $form.find('input[name="firstname"').val();
		      var lastName = $form.find('input[name="lastname"').val();
		      var email = $form.find('input[name="email"').val();
          window.location = "https://robertbiswas.com?firstname=" + firstName + "&lastname=" +lastName + "&email=" +email;
         }, 200);
    }
  });
</script>