api.js

import { AsyncStorage } from 'react-native';

const STORAGE_KEY = '@Flashcards:store';

export const getAllDecks = () =>
    AsyncStorage.getItem(STORAGE_KEY)
        .then(d => JSON.parse(d))
        .catch(err => {
            console.log(err);
            return [];
        });

export const saveDeckTitle = title =>
    AsyncStorage.getItem(STORAGE_KEY)
        .then(data => {
            data = JSON.parse(data);
            data = data ? data : {};
            data[title] = { title, questions: [] };
            return AsyncStorage.setItem(STORAGE_KEY, JSON.stringify(data));
        })
        .catch(err => {
            console.log(err);
            return null;
        });

export const getDeck = id =>
    AsyncStorage.getItem(STORAGE_KEY)
        .then(data => {
            data = JSON.parse(data);
            return data[id];
        })
        .catch(err => {
            console.log(err);
            return null;
        });

export const addCardToDeck = (title, card) =>
    AsyncStorage.getItem(STORAGE_KEY)
        .then(data => {
            data = JSON.parse(data);
            data[title].questions = data[title].questions.concat(card);
            return AsyncStorage.setItem(STORAGE_KEY, JSON.stringify(data));
        })
        .catch(err => {
            console.log(err);
            return null;
        });