Comment by Cthulhu_

> I joke that it was as if you took a monk, gave him a book about javascript, and then locked him in a cell for 10 years.

I've had a similar experience (see other comment), the original author was a junior developer at best, but unfortunately, a middle-aged, experienced developer, one of the founders of the company, and very productive. But obviously, not someone who had ever worked in a team or who had someone else work on their codebase.

Think functions thousands of lines long, nested switch/case/if/else/ternary things ten levels deep, concatenated SQL queries (it was PHP because of course), concatenated JS/HTML/HTML-with-JS (it was Dojo front-end), no automated tests of any sort, etc.