PaymentMethodChangeEvent - Web APIs
for example, if methodname is basic-card, indicating that the basic card payment method is being used for validation, the methoddetails field must be a basiccardchangedetails object.

Payment Request API - Web APIs
related dictionaries for the basic card specification basiccardchangedetails an object providing redacted address information that is provided as the methoddetails on the paymentmethodchange event sent to the paymentrequest when the user changes payment information.