I had to work that one out myself. Excellent

No doubt it is clever, never knew you could do it like this. Thans

nice

Nice

Its clever, but is it the best practice?

oh thats spicy

wtf is this man?

it seems my solution will come up soon

That's very clever, I didn't even think for a moment that it could be done this way :D

people will understand the power of regular expression by seeing this, it's really amazing, but i don't think this will be encouraged to be in used in production...

added

I also thought that would be cool to solve this using regex!

In my case I used join('') enstead of join('-') and solved the /222/ problem by checking how many numbers are behind like this /^(...)*2{3}

You can see full code here:
https://www.codewars.com/kata/reviews/525caa5c1bf619d28c000338/groups/61e41f559a04f80001a6b80a