app.js

buyButton.addEventListener('click', () => {

  const request = new PaymentRequest(buildSupportedPaymentMethodData(), buildShoppingCartDetails());
  request.canMakePayment().then(result => {

    if (result) {
      request.show().then(paymentResponse => {
        console.log(paymentResponse.details)
        // Here we would process the payment. For this demo, simulate immediate success:
        paymentResponse.complete('success')
          .then(() => thankYouMessage.style.opacity = 1)
      })
    }
    
  })
})