Download all of the files or clone this repo and run the ajaxy.html file. Open ajax.js to follow along with the tutorial. Note that data.json is not used at all in the "application" since we can't do GET HTTP requests from a local file. The file's there for reference.
Of course, Sir Arren already made a tutorial for AJAX. You can find it here. However, I thought of making a short and simple one as a primer so that you become familiar with the format.
Anyway, you don't have to check this if you don't have the time, but yeah. Cool.
signed, neal