index.js

import {
    NativeModules,
    Platform,
    PermissionsAndroid
} from 'react-native';

const RNGalleryManager = NativeModules.RNGalleryManager;

const GalleryManager = {
    /**
     * Get Assets from the gallery
     * @param {object} params           Object with params
     * @param {string} params.type      Type of the asset. Can be - image, video, all
     * @param {number} params.limit     Number of assets returned
     * @param {number} params.startFrom From which index to start
     * @param {string} params.albumName If requesting items from album -> set the album name
     */
    getAssets(params) {
        return RNGalleryManager.getAssets(params);
    },

    /**
     * To Request authorization for access photos
     * returns Promise
     */
    requestAuthorization(title, message) {
        if (Platform.OS === 'ios') {
            return RNGalleryManager.requestAuthorization();
        } else {
            return new Promise(async (resolve, reject) => {
                const granted = await PermissionsAndroid.request(PermissionsAndroid.PERMISSIONS.WRITE_EXTERNAL_STORAGE, {
                    title: title,
                    message: message,
                });

                // On devices before SDK version 23, the permissions are automatically granted if they appear in the manifest,
                // so check and request should always be true.
                // https://github.com/facebook/react-native-website/blob/master/docs/permissionsandroid.md
                const isAuthorized =
                    Platform.Version >= 23 ? granted === PermissionsAndroid.RESULTS.GRANTED : granted === true;

                if (isAuthorized) {
                    resolve({ isAuthorized: true });
                } else {
                    resolve({ isAuthorized: false })
                }
            });
        }

    },

    /**
     * Get List with album names
     */
    getAlbums() {
        return RNGalleryManager.getAlbums();
    },

    /**
     * Convert video
     */
    convertVideo(params) {
        return RNGalleryManager.convertVideo(params);
    }
}

module.exports = GalleryManager;