serving/helloworld-nodejs: Respect the PORT env var (#458)

Author: grayside

serving/samples/helloworld-nodejs/README.md

@@ -52,13 +52,13 @@ recreate the source files from this folder.
     app.get('/', function (req, res) {
       console.log('Hello world received a request.');
 
-      var target = process.env.TARGET || 'World';
-      res.send('Hello ' + target);
+      const target = process.env.TARGET || 'World';
+      res.send('Hello ' + target + '!');
     });
 
-    var port = 8080;
+    const port = process.env.PORT || 8080;
     app.listen(port, function () {
-      console.log('Hello world listening on port',  port);
+      console.log('Hello world listening on port', port);
     });
     ```
 

serving/samples/helloworld-nodejs/app.js

@@ -20,11 +20,11 @@ const app = express();
 app.get('/', function (req, res) {
   console.log('Hello world received a request.');
 
-  var target = process.env.TARGET || 'World';
-  res.send('Hello ' + target);
+  const target = process.env.TARGET || 'World';
+  res.send('Hello ' + target + '!');
 });
 
-var port = 8080;
+const port = process.env.PORT || 8080;
 app.listen(port, function () {
-  console.log('Hello world listening on port',  port);
+  console.log('Hello world listening on port', port);
 });