the fact that you can just redefine Map in a script is mind boggling
> false = 4
false = 4
^^^^^
Uncaught SyntaxError: Invalid left-hand side in assignment
Fascinatingly enough though, you can assign a value to NaN. It doesn't stick tho. > NaN
NaN
> NaN = 42
42
> NaN
NaN
>
(map behaves as described.)