The read-only methodName property of the PaymentMethodChangeEvent interface is a string which uniquely identifies the payment handler currently selected by the user. The payment handler may be a payment technology, such as Apple Pay or Android Pay, and each payment handler may support multiple payment methods; changes to the payment method within the payment handler are described by the PaymentMethodChangeEvent.

A string which uniquely identifies the currently-selected payment handler. This may be a string chosen from the list of standardized payment method identifiers, or a URL used by the payment processing service. See Payment method identifiers for more information.

The default value is the empty string, "".

This example uses the paymentmethodchange event to watch for changes to the payment method selected for Apple Pay, in order to compute a discount if the user chooses to use a Visa card as their payment method.

request.onpaymentmethodchange = (ev) => {
  const { type: cardType } = ev.methodDetails;
  const newStuff = {};
  if (ev.methodName === "https://apple.com/apple-pay") {
    switch (cardType) {
      case "visa": {
        // do Apple Pay specific handling for Visa card…
        // methodDetails contains the card information
        const discount = calculateDiscount(ev.methodDetails);
        Object.assign(newStuff, discount);
        break;
      }
    }
  }
  // finally…
  ev.updateWith(newStuff);
};
const response = await request.show();

Note that the methodDetails property is being used by the calculateDiscount() function to compute any payment discount, then updateWith() is called to update the event with the computed update.