I’ve uploaded NodeJS code to https://github.com/0xckylee/rn-node-firebase_stripe-payment-subscription. Please contact me through email (email@example.com) or DM on Twitter @0xckylee if you have any questions or need some explanations on code/implementation. For the React Native part, if you have an existing RN project I could help out based on how your project’s set up.
By the way, serving static files from backend frameworks is not recommended because of static files’ heavy network load; but this was the only (PCI-DSS compliant) workaround I could find at the moment given lack of safe payment libraries for RN and existing backend framework set up in the company. For other times, please try not to serve static files from backend!