It's resolved sequentially, so the first truthy value left to right and defaulting to whatever the last item is regardless of its value if all others are falsey.

Is using recursion best practices when there are other, reasonably consise ways to do it? The context im thinking of is best practices as a web dev.

This seemed difficult for 8kyu in JavaScript

Is commenting functions like this a best practices thing?

This seems like the most elegant solution - im impressed by the regex and wondering how it works.

Did you ever figure out what was happening with this? Why was it blowing up with large numbers?