I already have an app written in MERN stack with koa server prepared build version. My main node file to run by node server.js command to start the whole app looks like this.
In every tutorial, I see that I need to add functions.https.request etc. in the beginning of coding (or at least to suppose doing it).
How could I host my app on firebase the same as I could on heroku - with whole server side?
You can't deploy and run an arbitrary node app on Cloud Functions. You have to make use of the different types of triggers that are defined by the product.
See the Cloud Functions for Firebase main page to see the list.
- Cloud Firestore Triggers
- Realtime Database Triggers
- Firebase Authentication Triggers
- Google Analytics for Firebase Triggers
- Crashlytics Triggers
- Cloud Storage Triggers
- Cloud Pub/Sub Triggers
- HTTP Triggers