How to store API response in memory

export default class Category extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
            isLoading: false,
            categories: [],
            loaded:false,
            page: 1,
        };
    }

    static navigationOptions = {
        headerTitle: 'Categories',
        title: 'Categories',
    };

    componentDidMount() {
        this.fetchCategories();
    }

    fetchCategories() {
        this.setState({isLoading: true});
        categoryApi.getAll(this.state.page).then(response => {
            if (response.data) {
                console.log(response.data);
                this.setState({
                    categories: this.state.categories.concat(response.data),
                    isLoading: false,
                });
            } else {
                this.setState({isLoading: false});
                console.log(response);
                Alert.alert(
                    constants.app.errorTitle,
                    constants.app.errorMessage,
                    [],
                    {cancelable: true}
                )
            }
        });
    }

    componentWillMount() {

    }

    render() {
        const {navigate} = this.props.navigation;

        return (
            <View style={styles.container}>
                <View style={styles.projektiHeader}>
                    <Text style={styles.projekti}>VALITSE PROJEKTI</Text>
                </View>
                <View style={styles.categoriesList}>
                    <FlatList
                        data={this.state.categories}
                        extraData={this.state}
                        renderItem={(rowData) => <CategoryItem navigate={navigate} item={rowData}/>}
                        onEndReached={this.showMore}
                        keyExtractor={(item, index) => index}
                        // onEndReachedThreshold={0.5}
                    />
                </View>
                <View style={styles.shopsNear}>
                    <ShopsNear navigate={navigate}/>
                </View>
            </View>
        );
    }
}