btnLogin.addEventListener('click', e =>{
        const email = txtEmail.value;
        const pass = txtPassword.value;
        const auth = firebase.auth();
        const promise = auth.signInWithEmailAndPassword(email,pass);
        promise
        .then(user => window.location.href="http://www.example.com/" + user.uid + "/index.html")
        .catch(e => console.log(e.message));
    })

firebase.auth().onAuthStateChanged(firebaseUser => {
        if(firebaseUser){
            console.log(firebaseUser);
        }else{
            window.location.href = "http://www.example.com";
            console.log("offline");
                    }
});