paymentRequestShow.js

  //Show the Native UI
  payment.show()
  //When the promise is fulfilled, pass the results to your server for processing
  .then(result => {
    return process(result).then(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');
      }
    }).catch((err) => {
      console.error('User rejected request', err.message)
    }); 
  });