https://www.crisis.org.uk/Assets/uMarketingSuite/Scripts/uMarketingSuite.analytics.blockerdetection.js

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