The upgrades I did for the Team Makita website I hear are somewhat of a running joke at 4mation. Dubbed “tools js”, the upgrade allowed tradies to add their Makita products to their toolbox in order to claim points. Their were thousands of products which would make it hard to find the product to add, so I daisy chained drop down boxes so they could select their trade, which would filter the next drop down of categories, which would filter the next drop down of products which would filter to the next drop down of models and so on, this needed to happen without refreshing the page. I implemented some hooks in the 4mation shop which would dynamically generate a JS data file whenever a category or product was changed with all the tool data (what some might call JSON now).
A couple of months later another developer had to perform some maintenance on the project and I received word that the tools.js file was thousands of lines long. We all have to learn some how