My first kumite - I actually started this as a kata but wasn't sure if I should publish it. Didn't know what a 'kumite' was until just now. Still trying to think through test cases - especially https://docs.codewars.com/authoring/guidelines/submission-tests/#random-tests

Mutates in the input. Definitely not best practices.

I don't understand why people vote this for "Best Practices" when this is clearly don't.
The solution is good, but all of the solutions here are the some. The different is he don't use let for this variables, don't give them a propre names, leave his console.log in his submit solution, and don't use "Best Practice" style (he need to write his { in the same line, for example).

This is not a good solutions newbies need to learn from, especially when the second one (right below it) is much better (still not perfect).