We have so far shown callbacks and Promises. We went from the problem with callbacks, namely callback hell, and how Promises solved that. However, there is a library called async, which is an alternative to callbacks and promises. So why would we want to use the async library instead? The async library is meant to operate on collections in an asynchronous context. The library authors themselves say this about it:
Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript
So, if your asynchronous code starts to become unmanageable and you find yourself wanting to operate on asynchronous collections rather than a few calls here and there, this library might be for you. ...
