stripe registerElement not defined

I am trying to use Example2 from stripe

my jscript is

<script src="https://js.stripe.com/v3/"></script>
<script>
      var stripe = Stripe('test key');
      var elements = stripe.elements();
      example2.js per link above
</script>

I am getting an error on the last line of example2.js

registerElements([cardNumber, cardExpiry, cardCvc], 'example2'); (Not Defined)

Suggestions welcome.. thanks