async - Async utilities for node and the browser

Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript. Although originally designed for use with Node.js and installable via npm i async, it can also be used directly in the browser.

Async provides around 70 functions that include the usual 'functional' suspects (map, reduce, filter, each…) as well as some common patterns for asynchronous control flow (parallel, series, waterfall…). All these functions assume you follow the Node.js convention of providing a single callback as the last argument of your asynchronous function -- a callback which expects an Error as its first argument -- and calling the callback once.