Add Node.js client code

Author: Bacto

backend/package.json

@@ -6,6 +6,7 @@
   "dependencies": {
     "dotenv": "^6.2.0",
     "jsonwebtoken": "^8.5.1",
+    "eventsource": "^2.0.2",
     "request": "^2.88.0",
     "request-promise-native": "^1.0.5"
   },

backend/subscriber.js

@@ -0,0 +1,27 @@
+// This is a simple example of a Mercure-Hub client in Node.js.
+// This is not usual to connect from Node.js and you shouldn't probably using this code but use the example in "frontend" which will show you how to connect from a browser.
+const EventSource = require('eventsource');
+
+const endpoint = '<XXXXXX>.stackhero-network.com'; // PUT YOUR SERVER URL
+
+// Caution: this is not your subscriber JWT defined in Stackhero's console.
+// To get you subscriber JWS (with a final S, not T like in JWT), you have to generate it on the server side.
+// An example is available in the `backend/subscriberJwsGenerator.js`
+const subscriberJws = ''; // PUT YOUR SUBSCRIBER JWS
+
+
+const url = new URL('https://' + endpoint + '/.well-known/mercure');
+
+// Add topic to listen to
+url.searchParams.append('topic', `https://${endpoint}` + '/books/1');
+
+const eventSource = new EventSource(
+  url.toString(),
+  {
+    headers: {
+      Authorization: `Bearer ${subscriberJws}`
+    }
+  }
+);
+
+eventSource.onmessage = e => console.log(e);