Script to remove Amex and Discover from the list of valid credit cards for events with fees.

remove_amex_and_discover_from_events.html

<script type="text/javsacript">
// See: https://salsasupport.zendesk.com/entries/44958284
$(document).ready(function() {
    if (/checkout\.sjs\?event_KEY=\d+/.test(window.location.href)) {
        $('option[value="amex"]').remove();
        $('option[value="disc"]').remove();
    }
})
</script>