Hopefully, I did put my .env file in the right place, I wanna access variables in firebase.js file for authentication to keep my API secure.

.env file:-

Here is my firebase.js file:-

import { initializeApp } from "firebase/app";
import { getAuth } from "firebase/auth";

// Your web app's Firebase configuration
const firebaseConfig = {
    apiKey: process.env.API_KEY,
    authDomain: process.env.DOMAIN,
    projectId: process.env.PROJECT_ID,
    storageBucket: process.env.STORAGE_BUCKET,
    messagingSenderId: process.env.MSG_SENDER_ID,
    appId: process.env.APP_ID,
};

// Initialize Firebase
const app = initializeApp(firebaseConfig);
const auth = getAuth();

export { app, auth };

The error I’m getting 👇:-

How to use .env file here?

>Solution :

Add a prefix of REACT_APP to your variable names in your dotenv file.
Like REACT_APP_API_KEY and to access the value in your react file use process.env.REACT_APP_API_KEY and after making changes make sure to restart your react app.