So I have this structure:

> 
> collection(users) { document(unknownID){
>  collection(listings) }, document(anotherUnknownId){ collection(listings) }, }
> 
> 
> 

There will be many documents with unknownID how I should get those listings inside document with unknownID ?

```
const collectionRef = firestore().collection('users').doc(unknownID).collection('listings');

```

What to do with that unknownID, how to get every listings collection inside ? 
[![enter image description here](https://i.stack.imgur.com/rAkg1.png)](https://i.stack.imgur.com/rAkg1.png)