// add Login and Pay callbacks

 window.onAmazonPaymentsReady = () => {
   this.createButton(sellerId, scope, type, color, size, mountLocation);
 }

// if the OffAmazonPayments namespace is already available, call the callback manually - otherwise wait for Amazon to call it

if (typeof window.OffAmazonPayments !== 'undefined') {
  window.onAmazonPaymentsReady();
}

createButton(sellerId, scope, type, color, size, mountLocation) {

        window.OffAmazonPayments.Button(mountLocation, sellerId, {
            type,
            color,
            size,
            authorization: () => {
                const loginOptions = { scope };

                window.amazon.Login.authorize(loginOptions, this.onAuthorize);
            },
            onError: this.onError,
        });
    }
}