PaymentDetailsUpdate.shippingAddressErrors

The PaymentDetailsUpdate dictionary's shippingAddressErrors property, if present,  contains an AddressErrors object whose contents provide error messages for one or more of the values in the PaymentAddress specified as PaymentRequest.shippingAddress.

var addressErrors = PaymentDetailsUpdate.shippingAddressErrors;

An AddressErrors object, which contains DOMStrings describing errors in the properties of a PaymentAddress. For each property in PaymentAddress, a property by the same name is found in shippingAddressErrors if and only if a validation error occurred for that property. In that case, the property in shippingAddressErrors is a string describing the validation error, ideally including suggestions about fixing the error.