Angular 2 and Firebase Hosting Backend

I know that this is not exactly an ionic question, but I’m trying to setup Stripe payments and due to security issues, I need a backend on Node.js with Angular2. I ran into a likely very simple problem. I have all my working code in index.js in the main backend folder on Firebase hosting, and I have my public/index.html page which is now empty. I have all the needed npm packages. My problem is, when I from my App to my backend, how do I run the index.js file???

Thanks so much!!!