Reverse engineering XKCD 1190

Question

The latest (as of now) comic is titled "Time". It's a standard-looking comic though without much action, but the picture's alt title says "Wait for it.". I waited but nothing happened (tried in Opera and IE9) so I took a look at the page source.

Next to the picture's <img> tag there was a <script> which included the following URL:

http://imgs.xkcd.com/static/time07.min.js

I tried to make sense of it, but I can't figure it out. Can someone explain how it works and what was supposed to happen?

@Gilles: interesting! However, there doesn't seem to be much explanation on what exactly the script does, but more of "here's the URLs it fetches". I hope someone can post an overview of the script's main parts and how they interact. I, for one, am lost in all the callbacks and closures. — Igor Skochinsky, Mar 27 '13 at 01:58
Perhaps it is a social experiment and is counting how long a person will wait for the image to change? — d1str0, Mar 27 '13 at 21:59

score 9 · Accepted Answer · answered Mar 27 '13 at 21:50

Somebody at XKCD fora pasted a link to this gist which contains a deobfuscated and annotated source along with some explanations:

The main part of Javascript that drives xkcd's "Time" comic (http://xkcd.com/1190/), deobfuscated and annotated. The bulk of the script seems to be an implementation of EventSource - which, while important, is not terribly interesting for our purposes, so I've omitted it here. After some Googling around, I am in fact fairly certain that the EventSource implementation used here is https://github.com/Yaffle/EventSource - after minifying and beautifying that code, it looks very similar to what shows up in time07.min.js.

As far as I can tell, it has no magic in it and serves just as a simple way for the server to let the client know when there is a new image.

Reverse engineering XKCD 1190

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