how to loop multiple arrays in react native - reactjs

Question

I am actually want to iterate a collection in firestore which contains multiple documents, and i want to return the doc that contain field uid equal of my uid.
that's the data in firestore:
const { user } = this.props ;
console.log("getting user data: ", user )
that's my code:
render() {
const auth = this.props.auth;
console.log("getting user id: ", auth.uid);
const userData = user.map((item)=>(
(item.uid) = (auth.uid)
? <Text color="white" size={28} style={{ paddingBottom: 8 }}>
{ item.displayName } </Text>
: <Text color="white" size={28} style={{ paddingBottom: 8 }}> Error
</Text>
)
);
return (
<Block style={styles.profileTexts}>
{userData}
</Block>
)
}
const mapStateToProps = ( state ) => {
console.log("state firebase",state);
return{
auth: state.firebase.auth,
user: state.firestore.ordered.users,
}
}
const mapDispatchToProps = (dispatch) => {
return {
signOut: () => dispatch(signOut()),
}
}
export default compose(
connect(mapStateToProps, mapDispatchToProps),
firestoreConnect([
{ collection: 'users'},
]))(Profile)
But i got this error:
"TypeError: undefined is not an object (evaluating 'o.map')"

Answer 1

inside your map you are using assignment operator instead of comparison operator.
if you just want to return an item which is same as auth.uid use a filter instead
Create a function which returns the item.uid === auth.uid
userFn = () => {
const {user} = this.props;
const authUser = user.filter(item => {
return item.uid === auth.uid
})
if (authUser.length>1){
return <Text>{authUser[0].displayName}</Text>
}
else return <Text>Error</Text>
}
then inside return statement
return (
<View style={{flex:1,justifyContent:'center'}}>
{this.userFn()}
</View>
);

Answer 2

You use user in render() method, but I don't see where did you get them?
I think this can fix the problem.
render() {
const auth = this.props.auth;
console.log("getting user id: ", auth.uid);
const user = this.props.user // <=== add this line
const userData = user.map((item)=>(
...