If the input string, with leading whitespace and possible +/- signs removed, begins with 0x or 0X (a zero, followed by lowercase or uppercase X), radix is assumed to be 16 and the rest of the string is parsed as a hexadecimal number.
If the input string begins with any other value, the radix is 10 (decimal).

you need to specify radix to stay on the safe side

Don't just post your code for no reason...

Submitting a translation to this Kata.

Lua translation

Please review and approve

While your code works, you're using filter when you could use another method or a single loop.