I tried both and all working. What are the difference?

```
import firebase from 'react-native-firebase';

const defaultApp = firebase.app();

defaultApp.database().ref('foobar').once('value', (snapshot) => {
  // snapshot from default app
});

```

vs

```
import firebase from 'react-native-firebase';

firebase.database().ref('foobar').once('value', (snapshot) => {
  // snapshot from default app
});

```