Full blown example.

public/emulator.html

@@ -66,7 +66,7 @@
       };
 
       const emulatorInit = data => {
-        EJS_gameUrl = data.game;
+        EJS_gameUrl = `/api/v1/rom?id=${data.gameId}`;
         EJS_core = data.core;
         EJS_gameName = data.gameName;
 
@@ -88,34 +88,35 @@
         }
 
         const { message } = data;
-
         switch(message) {
           case 'init':
             emulatorInit(data);
             break;
 
+          case 'volume':
+            EJS_emulator.setVolume(data.volume);
+            break;
+
           default:
             console.error('Unknown message', message);
         }
       };
 
-      EJS_ready = (...args) => {
-        send({ message: 'ready', data: args });
+      EJS_ready = () => {
+        send({ message: 'ready' });
       }
 
-      EJS_onSaveState = (...args) => {
-        send({ message: 'save', data: args });
+      EJS_onSaveState = () => {
+        send({ message: 'save' });
       }
 
-      EJS_onLoadState = (...args) => {
-        send({ message: 'load', data: args });
+      EJS_onLoadState = () => {
+        send({ message: 'load' });
       }
 
-      EJS_onGameStart = (...args) => {
-        send({ message: 'start', data: args });
+      EJS_onGameStart = () => {
+        send({ message: 'start' });
       }
-
     </script>
-    <!-- <script src="https://cdn.emulatorjs.org/stable/data/loader.js"></script> -->
   </body>
 </html>