https://www.capital.edu/Assets/Umbraco.Engage/Scripts/umbracoEngage.analytics.blockerdetection.js

1(function() {
2    function runBlockerDetection() {
3        var domain = window.location.protocol + "//" + window.location.hostname;
4        if (document.referrer == null || document.referrer.indexOf(domain) !== 0) {
5            var img = document.createElement("img");
6            img.src = "https://www.google-analytics.com/__utm.gif";
7
8            img.addEventListener("load", success);
9            img.addEventListener("error", failure);
10
11            document.body.appendChild(img);
12
13            function failure() {
14                umbEngage("send", "event", "Tracking", "Blocked", "Google Analytics");
15                cleanup();
16            }
17
18            function success() {
19                umbEngage("send", "event", "Tracking", "Allowed", "Google Analytics");
20                cleanup();
21            }
22
23            function cleanup() {
24                document.body.removeChild(img);
25            }
26        }
27    }
28
29    if (window.umbEngage) {
30        runBlockerDetection();
31    } else {
32        document.addEventListener('umbracoEngageAnalyticsReady', runBlockerDetection);
33    }
34})();