Duplicate: https://www.codewars.com/kata/array-merge-every-n-items/discuss/javascript

If we get a 0 inset, what do we do? Blow up the universe?

Needs random tests. Some guides here:

• https://github.com/Codewars/codewars.com/wiki/Tutorial%3A-Create-Your-First-Kata#write-good-tests-and-utilize-both-fixed-and-random-test-cases
• https://github.com/Codewars/codewars.com/wiki/Kata-Best-Practices#testing