This is very impressive and cool. However I really don't think that parsing source code and manipulating is a very maintainable way to do this (and this as someone who writes Clojure for a living).
You could do exactly the same using very simple Knockout. It wouldn't be as funky, but it would be something you'd be happy to use in production.
I did something like this in my presentation[1] about Ember.
It uses Ember.js to maintain the state of the code samples and proved to be very stable. I don't have interactive sliders on specific values, but the code is parsed and run after every character the user types. e.g. you can change the size of the squid on this page[2] and see it reflected immediately on the right.
It isn't really intended for production use. Personally, I plan to use it to tweak values in games I write, because having to alt+tab, find, edit, alt+tab, refresh, restore state for every tiny tweak to the position of a UI element sucks.
Interesting implementation! I'm using CodeMirror tokens and regexs to make numbers scrubbable and hex colors pickable: http://tributary.io/tributary/2958568/
I've been wanting to explore the route you took more, especially for doing even more code modification. I'd like to let users click on a number and turn it into a variable, or have a special object where members are added to the global table. You can then create controls external to the code with that table and hide the code (good for presenting after you're done coding). Looking forward to checking out your code!
Unfortunately there's no type information in JS, so it's very difficult to extract range data from just the source. Just don't drag it into that range ;)
PS, I'm planning to implement a color picker for strings like 'rgba(200,0,234,0.4)'
The liveness of something like this can be rather useful actually.
I wrote a not-as-fancy "canvas explorer" with a live updating image that you can save snapshots of. [1] Wrote this just yesterday to let me programmatically make images for use elsewhere (I suck at drawing tools.) I'm already enjoying the "liveness" of it and the fact that all images are remembered in localStorage. It's really cool that this is so easy to do with JS.
Plain and simple (if you could ever call it that) exploratory programming? The sort that yields stuff like Jared Tarbell's stuff http://levitated.net/daily/index.html and many Chrome Experiments, etc.
http://www.khanacademy.org/cs/gear/1178931559
Read John Resig's blog post for more details: http://news.ycombinator.com/item?id=4382076