Apply asynchronous function to each item in array

forEachPromise.js

/**
 *
 * @param items An array of items.
 * @param fn A function that accepts an item from the array and returns a promise.
 * @returns {Promise}
 */
export default function forEachPromise(items = [], fn =  Promise.resolve) {
  return items.reduce(
    (promise, item) => promise.then(() => fn(item)),
    Promise.resolve()
  );
}