https://chicagosinfonietta.org/wp-content/plugins/chicagosinfoni/js/sp-checkout-scroll.js?ver=1790900216

1function spektrixGetIframeCoords(elem) {
2    var body = document.body;
3    var docEl = document.documentElement;
4
5    var box = elem.getBoundingClientRect();
6
7    var scrollTop = window.pageYOffset || docEl.scrollTop || body.scrollTop;
8    var clientTop = docEl.clientTop || body.clientTop || 0;
9    var top  = box.top +  scrollTop - clientTop;
10
11    return { top: Math.round(top) };
12}
13
14function scrollSpektrixIframe(iframeActiveElementOffset) {
15    var iframe = document.getElementById('SpektrixIFrame');
16    var spektrixIframeOffset = spektrixGetIframeCoords(iframe).top;
17
18    window.scrollTo(0, spektrixIframeOffset + iframeActiveElementOffset);
19}
20
21window.addEventListener('message', function(event) {
22    var allowedOrigins = [
23        /\.spektrix\.com(:\d+)?$/i,
24        /\.chicagosinfonietta\.org$/i
25    ];
26    if (allowedOrigins.some(regex => regex.test(event.origin))) {
27        try {
28            var message = JSON.parse(event.data);
29            var offset = message['spektrixOffset'];
30
31            if (offset && !isNaN(offset) && offset > 0) {
32                scrollSpektrixIframe(offset);
33            }
34        } catch (ex) {
35            return;
36        }
37    }
38} );