I call the general update example "letterfall". I find it is a good example to learn how to use a language to interop with D3.
In this case, I'm using Elm to generate the alphabet, randomize it, and send it out to D3. Big whoop, as that is only a few lines of code in the original, but that's okay by me, I learned loads doing this.
To run it, do:
elm-make src/Letterfall.elm --output=resources/js/letterfall.js
Then load up './resources/index.html' in a browser, firefox or chrome or whatever.