Initialization

config object: credentials

The config object provides the credentials that identify the Firebase project it is part of. The credentials are sent when interacting with Firebase services.

const firebaseConfig = {
    apiKey: "....",
    authDomain: ".....firebaseapp.com",
    projectId: "....",
    storageBucket: ".....firebasestorage.app",
    messagingSenderId: "....",
    appId: "....",
}

the app object

we compute and store a reference to app to provide it to services such as auth or firestore.

const app = initializeApp(firebaseConfig)

environments managed by Google: skip the config

On a server managed by Google, the admin SDK is automatically configured, so we initialize the app config-less:

const app = initializeApp() // on Google server