Web Payments API の更新

// Checking for instrument presence.
request.canMakePayment().then(handleInstrumentPresence).catch(handleError);

// Checking for instrument presence.
if (request.hasEnrolledInstrument) {
  // hasEnrolledInstrument() is available.
  request.hasEnrolledInstrument().then(handleInstrumentPresence).catch(handleError);
} else {
  request.canMakePayment().then(handleInstrumentPresence).catch(handleError);
}

// Checking for payment app availability without checking for instrument presence.
if (request.hasEnrolledInstrument) {
  // `canMakePayment()` behavior change corresponds to
  // `hasEnrolledInstrument()` availability.
  request.canMakePayment().then(handlePaymentAppAvailable).catch(handleError);
} else {
  console.log("Cannot check for payment app availability without checking for instrument presence.");
}

// Not implemented in Chrome 74 and older.
// There's no way to feature-detect this, so check a few
// older versions of Chrome that you're seeing hit your servers.
if (/Chrome\/((6[0-9])|(7[0-4]))/g.exec(navigator.userAgent) !== null) {
  return;
}

// Supported in Chrome 75+.
request.show(new Promise(function(resolveDetailsPromise, rejectDetailsPromise) {
  // Find out the exact total amount and call
  // `resolveDetailsPromise(details)`.
  // Use a 3 second timeout as an example.
  window.setTimeout(function() {
    resolveDetailsPromise(details);
  }, 3000); // 3 seconds.
}))
.then(handleResponse)
.catch(handleError);

// In service worker context, `self` is the global object.
self.addEventListener('paymentrequest', (evt) => {
  evt.respondWith(new Promise((confirmPaymentFunction, rejectPaymentFunction) => {
    if (evt.changePaymentMethod === undefined) {
      // Not implemented in this version of Chrome.
      return;
    }
    // Notify merchant that the user selected a different payment method.
    evt.changePaymentMethod('https://paymentapp.com', {country: 'US'})
    .then((responseFromMerchant) => {
      if (responseFromMerchant === null) {
        // Merchant ignored the 'paymentmethodchange' event.
        return;
      }
      handleResponseFromMerchant(responseFromMerchant);
    })
    .catch((error) => {
      handleError(error);
    });
  }));
});

if (request.onpaymentmethodchange === undefined) {
  // Feature not available in this browser.
  return;
}

request.addEventListener('paymentmethodchange', (evt) => {
  evt.updateWith(updateDetailsBasedOnPaymentMethod(evt, paymentDetails));
});