https://pulsastar.com/Scripts/FeatureTest.js

1function failFeatureTest(title, message)
2{
3    document.getElementById("modaltitle").innerText = title || "Outdated Browser";
4    document.getElementById("modalmessage").innerText = message || "AMP cannot run on this system because your browser is too outdated, and doesn't support features used by modern web applications.";
5    document.getElementById("modalsubtitle").innerText = "Please use a newer browser to use AMP.";
6    document.getElementById("mainModal").style.backgroundColor = "black";
7    document.getElementById("mainModal").style.display = "block";
8    document.getElementById("relatedLinkA").innerText = "Browser-Update.org";
9    document.getElementById("relatedLinkA").href = "https://browser-update.org/update.html";
10    document.getElementsByClassName("modalpanel")[0].classList.add("visible");
11    document.getElementById("modalAdvanced").style["display"] = "none";
12    throw new Error("Outdated Browser");
13}
14
15if (document.addEventListener === undefined)
16{
17    failFeatureTest();
18}
19
20const isIE11 = !!window.MSInputMethodContext && !!document.documentMode;
21
22if (isIE11)
23{
24    failFeatureTest("Unsupported Browser", "AMP cannot run on Internet Explorer 11 as it does not support asynchronous javascript operations. Please either use Edge (Windows 8.1/Server 2012 R2+ Users) or another supported browser such as Firefox or Chrome.");
25}