Refactor to test

[CodingCarlos]

Low priority, since this works, but... well, we're here for the code, and the current version is such a mess.

This had been a fast (but working) first approach. I did not want to add any kind of dependency yet, since I did not have time to think about what's the best choice.

So, maybe the best option is just a template render as handlebars might work, or maybe some gulp plugins, or maybe using webpack with babel to make a cool es6 code modularized, or... I don't know. That's why this is an issue 🤣