Learning New Things

Today was an average afternoon – taking way too long to accomplish a seemingly trivial task, but looking up and learning a bunch of new things along the way. It seems there should be a better/easier (almost automatic, transparent) way to track the sources (links/pages), process (things tried) and results (code fragments)….

The basic goal in this case was to automate some execution of some javascript on a page. Because execution of the script caused a page load, it wasn’t a matter of writing the calls into the console. The faster and easier way would have been to write a Greasemonkey or Chrome Extension script (because there were timing issues, the script would have to write a time-based state file on actions), however, I figured I would try to see what kind of options were available with a control-script oriented model, as having that handy would be more generally useful in the future (more and more, straight mechanize is less useful as more JS proliferates).

Before getting started, I had to strip out just the lines that I wanted. I always forget how to do it, but that was a simple vim command lookup.

I looked at Selenium and Selenium RC, which probably would have worked fine (but that I didn’t use because I didn’t want to install extensions and the RC docs weren’t directly linked, but would have probably saved me time in the end).

Instead I decided to try out Watir (cross-platform, cross-browser, and my Ruby is rusty so this was a good excuse). I started out with SafariWatir, however, after a bit of poking, came up with a dead end on executing JavaScript. There’s a scripter object, but even after getting access to it via monkey-patching (did I mention my Ruby-fu sucks?), I was still getting errors and there wasn’t much help In general.

Instead of slogging through a potentially losing battle, I decided to jump ship to FireWatir. FireWatir uses JSSh, which communicates directly via JavaScript to Firefox, so it seemed like it might be a surer thing. My Firefox profiles were corrupted from my last system transfer, so there was a bit of messing with the profile folder until I gave up and started a new, but after that it seemed like I was home free.

Except, that when running js_eval, it turns out the scope that JSSh puts you in, isn’t in the document DOM, but rather the browser’s XUL DOM. For whatever reason, I couldn’t find a reference for even with the direct object type refereces (i.e. getWindows and getBrowser return ChromeWindow objects, which just don’t seem to have docs. Introspection via domDump() or inspect() just returned a huge amount of stuff to go through). Luckily, while searching, one of the results that turned up was a StackOverflow question on firewatir + jQuery which answered the question – ChromeWindow.content gets you into the HTMLDocument DOM. I’m a bit mystified why this isn’t in the firewatir or JSSh docs, as this seems to be one of the most common things that people would want to do, but well, that is the life of the developer…