This is very cool. But are you aware that your implementation of map returns an empty list if the first element in the array is false?

map([0, 1, 2], function(n){ return n+1 })
[]

And because it’s recursive, it stops at the first false element in the array.

map([1, 2, 0, 3, 4], function(n){ return n+1 })

[2, 3]