This was a freelance project, and I don't actually know where this lives, so I will point to my own code that I sent the client when I was done.
The client wanted an interactive map of the US showing demographic data.
The data was in Excel. I converted it to JSON, but this was not a smooth process because of how the data was structured in the spreadsheet. So I basically wrote a script that spit the data out (literally on a webpage) as an object so that I could copy and paste it into a JS file and use that as a pseudo-API.
The rest was just using HTML and vanilla JS to make it work like the mockup.