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Properly stop a Firebase app in Node.js

Normally, the Node.js process will exit when there is no work scheduled (docs). You shouldn’t call process.exit() unless it is necessary to terminate the Node.js process immediately due to an error condition. Calling process.exit() doesn’t let pending events to complete which may lead to unpredictable results as demonstrated in the docs.

Now that we know how to naturally terminate a Node.js application, how do we achieve it if we are using the Firebase JavaScript SDK?

First you need to cancel any asynchronous listeners. For example, if you subscribed for data changes, you need to unsubscribe:

let func = firebase.database().ref(userDB).on("value", myHandler);
firebase.database().ref(userDB).off("value", func);

Some people suggest that you also call firebase.database().goOffline() in the final stage.

Additionally, as described in these bug reports (#1 and #2), if you used firebase.auth() you need to call firebase.auth().signOut().

And finally, you also need to destroy the Firebase application by calling app.delete().

This has worked for me using Node.js version 10 and Firebase JS SDK version 8.