Check out and please back the Light Table project for JavaScript and Clojure: http://www.kickstarter.com/projects/ibdknox/light-table, which attempts to do some of what Bret was demonstrating. From the site: Light table is based on a few guiding principles: You should never have to look for documentation Files are not the best representation of code, just a convenient serialization. Editors can be anywhere and show you anything - not just text. Trying is encouraged - changes produce instantaneous results We can shine some light on related bits of code