payment-request.html

<html>
  <head>
  </head>
  <body>
    <button id="checkout">Buy</butoon>
    <script>
      function() startPaymentRequestCheckout {
        var methodData = [
          {
            supportedMethods: ['basic-card'],
            data: {
              supportedNetworks: ['visa', 'mastercard', 'amex'],
              supportedTypes: ['credit']
            }
          }
        ];

        var details =  {
          displayItems: [
            {
              label: "Sub-total",
              amount: { currency: "USD", value : "100.00" }, // US$100.00
            },
            {
              label: "Sales Tax",
              amount: { currency: "USD", value : "9.00" }, // US$9.00
            }
          ],
          total:  {
            label: "Total due",
            amount: { currency: "USD", value : "109.00" }, // US$109.00
          }
        };

        var options = {
          requestShipping: true 
        };

        //constructor
        var request = new PaymentRequest(methodData, details, options);

        //Show the Native UI
        request.show()

        //When the promise is fulfilled, pass the results to your server for processing
        .then(result => {
          return process(result).then(response => {
            // Examine server response
            if (response.status === 200) {
              //Show that the transaction was successful in the UI
              return result.complete('success');
            } else {
              //Show in the Native UI that the transaction failed
              return result.complete('fail');
            }
          })
        });
        request.addEventListener("shippingaddresschange", function (changeEvent) {
          // Process shipping address change
        });
        request.addEventListener("onshippingoptionchange", function (changeEvent) {
          // Process shipping option change (e.g. "one day shipping")
        });
      }
      document.getElementById('#checkout').addEventListener('click', startPaymentRequestCheckout)
    </script>
  </body>
</html>