Some useful firebase function that I use regularly

firebase.js

// Import the functions you need from the SDKs you need
import * as firebase from "firebase";
import "firebase/auth";
import "firebase/firestore";

// import "firebase/auth";
// import "firebase/analytics";

// TODO: Add SDKs for Firebase products that you want to use
// https://firebase.google.com/docs/web/setup#available-libraries

// Your web app's Firebase configuration
// For Firebase JS SDK v7.20.0 and later, measurementId is optional
const firebaseConfig = {
  apiKey: YOUR_KEY,
  authDomain: YOUR_KEY,
  projectId: YOUR_KEY,
  storageBucket: YOUR_KEY,
  messagingSenderId: YOUR_KEY,
  appId: YOUR_KEY,
  measurementId: YOUR_KEY,
};

// Initialize Firebase
let app;
if (firebase.apps.length === 0) {
  app = firebase.initializeApp(firebaseConfig);
} else {
  app = firebase.app();
}

const auth = firebase.auth();
const db = firebase.firestore();

export { auth, db };

functions.js

import { auth, db } from "../utils/firebase.js";

// used for logging in
  const handleLogin = async () => {
    await auth
      .signInWithEmailAndPassword(email, password)
      .then((userCredential) => {
        // Signed in
        var user = userCredential.user;

        console.log("test the user:", user);
        // ...
      })
      .catch((error) => {
        var errorCode = error.code;
        var errorMessage = error.message;

        console.error("test the user:", errorCode, errorMessage);

        // ..
      });


  };
// used for creating account
  const handleSignup = async () => {
    await auth
      .createUserWithEmailAndPassword(email, password)
      .then(async (userCredential) => {
        console.log("email, password", email, password);
        // Signed in
        console.log("tete", userCredential);
        var user = userCredential;

        await db.collection("users").doc(user.user.uid).set({
          email: email.toLowerCase().trim(),
          uid: user.user.uid,
          name: "test",
        });

        console.log("test the user:", user);
        // ...
      })
      .catch((error) => {
        var errorCode = error.code;
        var errorMessage = error.message;

        console.error("test the user:", errorCode, errorMessage);

        // ..
      });
  };


// get single user data
const getUserData = async () => {
    console.log("auth.currentUser.uid", auth.currentUser.uid);
    db.collection("users")
      .doc(auth.currentUser.uid)
      .get()
      .then((data) => {
        if (data.exists) {
          console.log("Document data:", data.data());
          setUser(data?.data());
        } else {
          // doc.data() will be undefined in this case
          console.log("No such document!");
        }
      })
      .catch((error) => {
        console.log("Error getting document:", error);
      });
  };
  
//  check if login than navigate

  useEffect(() => {
    auth.onAuthStateChanged((user) => {
      if (user) {
        // User is signed in, see docs for a list of available properties
        // https://firebase.google.com/docs/reference/js/firebase.User
        var uid = user.uid;
        navigation.reset({ index: 0, routes: [{ name: "Home" }] });
        // ...
      } else {
        // User is signed out
        // ...
      }
    });
  }, []);