Expo MapView with Marker React Hooks

MapScreen.js

import * as React from 'react'
import MapView from 'react-native-maps'
import * as Location from 'expo-location'
import * as Permissions from 'expo-permissions'
import { StyleSheet } from 'react-native'
import { Text } from 'react-native-paper'

const { useState, useEffect } = React

export default function MapScreen() {

    const [ locationResult, setLocation ] = useState( null )
    const [ mapRegion, setRegion ] = useState( null )
    const [ hasLocationPermissions, setLocationPermission ] = useState( false )

    useEffect( () => {
        const getLocationAsync = async () => {
            let { status } = await Permissions.askAsync( Permissions.LOCATION )
            if ( 'granted' !== status ) {
                setLocation( 'Permission to access location was denied' )
            } else {
                setLocationPermission( true );
            }

            let { coords: { latitude, longitude } } = await Location.getCurrentPositionAsync({})
            setLocation( JSON.stringify( { latitude, longitude } ) )
            
            // Center the map on the location we just fetched.
            setRegion( { latitude, longitude, latitudeDelta: 0.0922, longitudeDelta: 0.0421 } );
        }

        getLocationAsync()
    } )

    if ( locationResult === null ) {
        return <Text>Finding your current location...</Text>
    }

    if ( hasLocationPermissions === false ) {
        return <Text>Location permissions are not granted.</Text>
    }

    if ( mapRegion === null ) {
        return <Text>Map region doesn't exist.</Text>
    }

    return (
            <MapView
                style={ styles.container }
                region={ mapRegion }
                initialRegion={{
                    "latitude": 39.97343096953564,
                    "latitudeDelta": 0.0922,
                    "longitude": -75.12520805829233,
                    "longitudeDelta": 0.0421,
                }}
                onRegionChange={ region => setRegion( region )}
            >
                <MapView.Marker
                    title="YIKES, Inc."
                    description="Web Design and Development"
                    coordinate={{"latitude":39.969183,"longitude":-75.133308}}
                />
            </MapView>
    )
}

MapScreen.navigationOptions = {
    header: null
}

const styles = StyleSheet.create({
    container: {
      flex: 1,
    },
})