/*
 * Copyright (C) 2019 CZ.NIC z.s.p.o. (http://www.nic.cz/)
 *
 * This is free software, licensed under the GNU General Public License v3.
 * See /LICENSE for more information.
 */

/** Return undefined if object has no keys, otherwise return object. */
export function undefinedIfEmpty(instance) {
    if (Object.keys(instance).length > 0) {
        return instance;
    }
    return undefined;
}

/** Return object without keys that have undefined value. */
export function withoutUndefinedKeys(instance) {
    return Object.keys(instance).reduce((accumulator, key) => {
        if (instance[key] !== undefined) {
            accumulator[key] = instance[key];
        }
        return accumulator;
    }, {});
}

/** Return copy of passed object that has only desired keys. */
export function onlySpecifiedKeys(object, desiredKeys) {
    return desiredKeys.reduce((accumulator, key) => {
        accumulator[key] = object[key];
        return accumulator;
    }, {});
}