Add beforeunload event to add confirmation dialog when leaving page (#6279)

js/main.js

@@ -600,4 +600,15 @@ headerBar.addEventListener("click", (e) => {
   }
 });
 
+//------------------------------------------------
+// Add a confirmation dialog when leaving the page
+// Useful to avoid data loss
+//------------------------------------------------
+window.addEventListener('beforeunload', function (event) {
+  // Cancel the event
+  event.preventDefault();
+  // Chrome requires returnValue to be set
+  event.returnValue = '';
+});
+
 moveToChatTab();