Description:

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

Async provides around 20 functions that include the usual 'functional'
suspects (map, reduce, filter, forEach…) 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 async function.