Deploying the Node.js application to Heroku would involve the following command:

//assumes you have ran $ heroku apps:create ltngOutApp 
git add

git commit -m "Lightning Out App"
git push heroku master

On successful build, you can open the Heroku app from a Terminal using the heroku open command. 

Configure CORS for the Heroku URL, as shown in the following screenshot in your Salesforce instance. CORS can be found by navigating to Set up | Security Controls | CORS.

The application will ask for credentials and, once logged in, you will see the YouTube search component functional on the Heroku instance, as shown in the following screenshot: