auth.js

// Your web app's Firebase configuration
var firebaseConfig = {
    apiKey: "AIzaSyDqJV3PB3fDfYUsk8Q2HbnbvE7SoQs-DWE",
    authDomain: "project-muscle-e3d84.firebaseapp.com",
    projectId: "project-muscle-e3d84",
    storageBucket: "project-muscle-e3d84.appspot.com",
    messagingSenderId: "182910615574",
    appId: "1:182910615574:web:5645114f6dde5674cd3537",
    measurementId: "G-EKVRD04K2W"
};
// Initialize Firebase
firebase.initializeApp(firebaseConfig);

//Get Elements
const txtEmail = document.getElementById("txtEmail");
const txtPassword = document.getElementById("txtPassword");
const btnLogin = document.getElementById("btnLogin");
const btnSignup = document.getElementById("btnSignup");

//Add Login Event
btnLogin.addEventListener('click', e => {
    const email = txtEmail.value;
    const password = txtPassword.value;

    const auth = firebase.auth();

    //sign in with firebase auth
    auth.signInWithEmailAndPassword(email, password).then(user => {
        alert("Login Successful :)");
    }).catch(err => {
        alert(err.message);
    });

});



//Add Signup Event
btnSignup.addEventListener('click', e => {

    //get email and password
    const email = txtEmail.value;
    const password = txtPassword.value;
    const auth = firebase.auth();

    //sign in with firebase auth
    const promise = auth.createUserWithEmailAndPassword(email, password).then(user => {

        var user = firebase.auth().currentUser;

        user.updateProfile({
            displayName: "Jane Q. User"
        }).then(function () {

            alert("Signup Successful :) " + user.displayName)

            window.location.href = "index.html"

            document.getElementById("sign-in").style.display = "none";


        }).catch(function (error) {
            // An error happened.
        });

    })

});



firebase.auth().onAuthStateChanged(firebaseUser => {
    if (firebaseUser) {
        console.log(firebaseUser);
        btnLogOut.classList.remove('hidden');
        btnLogin.classList.add('hidden');
    } else {
        console.log('not logged in');
        btnLogOut.classList.add('hidden');
        btnLogin.classList.remove('hidden');
    }
});