how to delete whole flatlist in one go and whole firestore collection

1deleting whole flatlist in one go using firestore 
2
3filter data=(_item)=>{
4   this.setState({users: this.state.users.filter(item => item. Key=== _item)});
5    console.log(this.state.favorites) }
6call this function in button deleteall code given below
7 <Touchable Opacity
8            onPress={() => {   async function massDeleteUsers() {
9              // Get all users
10              const usersQuerySnapshot = await firestore().collection('user').get(                 
11              );             
12              // Create a new batch instance
13              const batch = firestore().batch();             
14              usersQuerySnapshot.forEach(documentSnapshot => {
15                batch.delete(documentSnapshot.ref); });             
16              return batch.commit();}             
17           massDeleteUsers().then(() =>{     
18             this.filterdata()
19               console.log('All users deleted in a single batch operation.')}) }}>
20so this will delete whole flatlist in on go and delete whole firestore collection