Warning: It looks like you're using the development build of the Firebase JS SDK

The proper way to import firebase is as such:

import firebase from 'firebase/app';
import 'firebase/database'; // If using Firebase database
import 'firebase/storage';  // If using Firebase storage

The proper way to import firebase and getting rid of the warnings is:

Always import this way

import firebase from 'firebase/app';

Then import each sub-modules (each firebase service) as needed

import 'firebase/auth';        // for authentication
import 'firebase/storage';     // for storage
import 'firebase/database';    // for realtime database
import 'firebase/firestore';   // for cloud firestore
import 'firebase/messaging';   // for cloud messaging
import 'firebase/functions';   // for cloud functions

The warning is rather informative and lays out exactly what you need to do. In your case, this is the line thats telling you to switch up the way you are importing your files:

ES Modules: import firebase from 'firebase/app'; import 'firebase/';

In your fire.js file try changing this:

import firebase from 'firebase'

To this:

import firebase from 'firebase/app'

That should clear it up!

Side note:

In my case I was using firestore so I had an additional import that I also changed from:

import firestore from 'firebase/firestore'

To:

import 'firebase/firestore'