DefinitelyTyped/types/googlepay/googlepay-tests.ts

const allowedCardNetworks = new Array<google.payments.api.AllowedCardNetwork>(
    'AMEX',
    'DISCOVER',
    'JCB',
    'MASTERCARD',
    'VISA',
    'INTERAC'
);

const allowedPaymentMethods = new Array<google.payments.api.PaymentMethod>({
    type: 'CARD',
    parameters: {
        allowedAuthMethods: ['PAN_ONLY', 'CRYPTOGRAM_3DS'],
        allowedCardNetworks,
        billingAddressRequired: true,
        billingAddressParameters: {
            format: 'MIN'
        }
    }
});

const tokenizationSpecification: google.payments.api.PaymentMethodTokenizationSpecification = {
    type: 'PAYMENT_GATEWAY',
    parameters: {
        gateway: 'example',
        gatewayMerchantId: 'abc123'
    }
};

const getGooglePaymentsClient = (env?: google.payments.api.EnvironmentType) => new google.payments.api.PaymentsClient({ environment: env });

function onGooglePayLoaded() {
    const client = getGooglePaymentsClient();

    client.isReadyToPay({
        apiVersion: 2,
        apiVersionMinor: 0,
        allowedPaymentMethods
    }).then(response => {
        if (response.result) {
            addGooglePayButton();
            prefetchGooglePaymentData();
        }
    }).catch(err => {
        console.error(err);
    });
}

function addGooglePayButton() {
    const buttonOptions: google.payments.api.ButtonOptions = {
        onClick: onGooglePaymentButtonClick,
        buttonColor: 'black',
        buttonType: 'short',
    };
    const client = getGooglePaymentsClient();
    const button = client.createButton(buttonOptions);
    document.appendChild(document.createElement('div').appendChild(button));
}

function getGooglePaymentDataConfiguration(): google.payments.api.PaymentDataRequest {
    return {
        apiVersion: 2,
        apiVersionMinor: 0,
        merchantInfo: {
            merchantId: '01234567890123456789'
        },
        transactionInfo: {
            totalPriceStatus: 'FINAL',
            totalPrice: '123.45',
            currencyCode: 'USD'
        },
        allowedPaymentMethods,
        shippingAddressRequired: true
    };
}

function prefetchGooglePaymentData() {
    const client = getGooglePaymentsClient();
    client.prefetchPaymentData(getGooglePaymentDataConfiguration());
}

function onGooglePaymentButtonClick() {
    const request = getGooglePaymentDataConfiguration();
    const client = getGooglePaymentsClient();

    client.loadPaymentData(request)
        .then(data => console.log(data))
        .catch(err => console.error(err));
}