Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/tools/js/Shared/utils/MobileMessenger/utils.ts

@@ -0,0 +1,19 @@
+import { MobileMessage } from "./typings";
+
+/**
+ *
+ * @param message
+ */
+export function sendMessage(message: MobileMessage): void {
+  if ((window as any)?.webkit?.messageHandlers?.mobileApp?.postMessage) {
+    // This should not be stringify'd because iOS is fine with objects
+    // https://github.com/DnDBeyond/ddb-character-tools-client/pull/306
+    (window as any).webkit.messageHandlers.mobileApp.postMessage(message);
+    return;
+  }
+
+  if ((window as any)?.mobileApp?.postMessage) {
+    (window as any).mobileApp.postMessage(JSON.stringify(message));
+    return;
+  }
+}