Async JavaScript

Chapter 3Promises and Deferreds

In 2010, I had this conversation with my prolific colleague Mr. Ajax:

Me:

Hey, would you fetch some data from this URL for me, please?

Mr. Ajax:

I’m on it! Just give me a success callback so I can let you know when I’m done.

Me:

OK, here you go. Thanks.

Mr. Ajax:

Oh, and you should give me an error callback, too. You know, just in case.

Me:

Good point. Anything else?

Mr. Ajax:

Hey, I noticed that there’s some code duplication between those two callbacks! You could move that into a third always callback.

Me:

(impatiently) Alright, I’ll refactor them. Tell you what: why don’t you run now, and I’ll give you the callbacks later?

Mr. Ajax:

(irately) What do I look like, an EventEmitter?

Thankfully, jQuery ...