I have been messing around in JavaScript and d3.js a bit more than usual lately.
In the past my JavaScript prototyping environment was a collection of html/js/json files on my local disk and a basic HTTP server (like python SimpleHTTPServer). I would edit files and reload reload reload reload. Very tiresome. Not very "2014" if you ask me.
Well I have seen the light, there are a few ways to skin this cat and get into a more robust and interactive development environment.