This kata would really benefit from some example test cases for JS. I'd be happy to create some!

Checking for a null input seemed a bit out of scope and tedious. I think removing it would help solvers stay focused on the actual problem.

I would love to see an unconstrained version of this kata (ie. Find the longest path the spy could take based on these ticket purchases)

This solution is incredibly difficult to read.

I can't determine the intended function signature for JS. Please explicitly clarify this in the description and/or create example test cases.

hahaha!

This is nearly impossible to read.

This seems to be a duplicate of https://www.codewars.com/kata/basic-mathematical-operations