I finally got top answer.

looove this solution, beautifully formated, easy to understand, and modify.

That because the pattern is strongly checking for only digit (0 - 9) nothing else

I'm not too sure, but I think these builtins are internally written in C, making them automatically blazing fast. Calling the solution "horribly inefficient" is really dramatic. On the grand scheme of things, this is still an O(n) solution. It is also incredibly readable. I have run some cursory benchmarks and the "inefficient" method gobsmacks yours for all list lengths I've tried (we're talking around more than 3x faster than yours). Take this with a grain of salt since they're informal tests, but it should hopefully make you reconsider making hasty performance comments in the future. I'll attach it spoilered below.

can't think of any other solution

Esta bueno era lo que se aprendio en el dia jeje

love it

why I always specify "0" in range()?

damn you regex !!!

Yup.

OMG

Tests now use assert.deepEqual plus reply above makes such question obsolete

personally I allways prefer braces. Makes arguments for methods much more readable.