Cannot export firebase-admin's initializeApp function

In an attempt to abstract the firebase-admin dependency, I have a file index.js that is meant to export the functionality my project uses. Why is it not possible to export the initializeApp as a property?

For example:

index.js

const firebaseAdmin = require('firebase-admin');

exports.initializeApp = firebaseAdmin.initializeApp;

consumer.js

const firebaseAdmin = require('path/to/index.js');

firebaseAdmin.initializeApp();

The following error is thrown:

TypeError: Cannot read property 'initializeApp' of undefined

In an attempt to isolate the issue, I wrote the following to prove that initializeApp cannot be exported as a property, as I've done with other functions:

const firebaseAdmin = require('firebase-admin');

const initializeApp = firebaseAdmin.initializeApp;

initializeApp();

This throws:

TypeError: Cannot read property 'INTERNAL' of undefined

Why can I not export initializeApp as a property? This error has forced me to rewrite the export in index.js to:

exports.initializeApp = () => firebaseAdmin.initializeApp();

But this feels like a hack.

Does it make a difference that every one of my files starts with 'use strict;'? That would be surprising.

Solution

This is a result of how the Admin SDK is implemented. The main export of the Admin SDK package is not a real module, but an instance of a class. So when you extract a single method from that class instance, it looses all its context, and internal references like this starts malfunctioning. Here's a simplistic example to illustrate the problem.

// file: sdk.ts
class Firebase {
  public INSTANCE = {key: 'sdk'};

  public initializeApp() {
    console.log('Initializing', this.INSTANCE['key']);
  }
}

const admin = new Firebase();
export = admin;

# File: test.js
// admin actually points to an instance of the Firebase class
const admin = require('./sdk');

// extract a single method from the object instance
const initializeApp = admin.initializeApp;

// The "this" reference in the initializeApp method no longer works
initializeApp();

You will have to continue using the workaround you've found for now. It might get addressed in a future release of the SDK, but right now it's not supported.