Some instructional comments for index.worker.js

src/plot/index.worker.js

@@ -1,5 +1,13 @@
 onmessage = function(event) {
+
+  // event.data is an object from the community page
+  // the type property tells you what kind of message is sent
+
   if (event.data.type === 'ping') {
+
+    // use postMessage() to send anything you want back
+    // to the main community page!
+
     postMessage('Pinged: ' + event.data.value);
   }
-};
+};