nice

Very easy to read. good stuff!

Enjoyed reading this one :)

Added, updated to node 12 as well

The use of match for splitting the 0:s and 1:s was very nice

I'm a little confused by the use of let over const, but I really like how straightforward this solution is. Very easy to read.

How would you suggest updating Javascript translation?

Is it bad practice to throw errors without handling them or just bad practice to throw them period? I happened upon your comment and I ended up searching the internet for clarification :)

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

Agreed.
https://www.codewars.com/kata/reviews/5ade1c91f806c60d6e00018b/groups/5ae97bdb268783fe61001cb6

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.