Checkout
    
    cancel
cancel Callback
The cancel callback is invoked when the payer choose to cancel a payment.
Usage
The cancel callback must be defined using the data-cancel attribute
            on the Checkout
            script tag. The attribute value may be the name of a global function or a URL string.
Example
<html>
    <head>
        <script src="https://ap-gateway.mastercard.com/checkout/version/27/checkout.js"
                data-cancel="cancelCallback"></script>
        <script type="text/javascript">
                function cancelCallback() {
                    //handle payment being cancelled
                }
        </script>
    </head>
    ...
</html>
    <html>
    <head>
        <script src="https://ap-gateway.mastercard.com/checkout/version/27/checkout.js"
                data-cancel="http://[your domain]/cancelPage"></script>
    </head>
    ...
</html>
Arguments
None
Return Value
None