firebase auth sign out javascript

firebase.auth().signOut().then(function() {
  console.log('Signed Out');
}, function(error) {
  console.error('Sign Out Error', error);
});
 Future<Null> _signOut() async {
    await _auth.signOut();
    this.setState(() {
      isLoading = false;
    });
    Navigator.of(context).pushAndRemoveUntil(
        MaterialPageRoute(builder: (context) => MyApp()),
        (Route<dynamic> route) => false);
  }