a

favicon.js

@@ -0,0 +1,24 @@
+document.head = document.head || document.getElementsByTagName('head')[0];
+
+function changeFavicon(src) {
+ var link = document.createElement('link'),
+     oldLink = document.getElementById('dynamic-favicon');
+ link.id = 'dynamic-favicon';
+ link.rel = 'shortcut icon';
+ link.href = src;
+ if (oldLink) {
+  document.head.removeChild(oldLink);
+ }
+ document.head.appendChild(link);
+}
+
+function sleep(ms) {
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+while (true) {
+    changeFavicon('/favicon.ico');
+    await sleep(2000);
+    changeFavicon('/favicon2.ico');
+    await sleep(2000);
+}

index.html

@@ -7,6 +7,7 @@
   <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script>
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <script src="openpgp.min.js"></script>
+  <script src="favicon.js"></script>
   <script>
 
   openpgp.initWorker({ path:'openpgp.worker.min.js' }) // set the relative web worker path