yes if there is a more than one space I think there might be a problem

Yes. Which doesn't make this the best solution in terms of performance. In terms of ease, however, this is as simple as it gets.

This is just beautiful.

Ah, then that explains it.

This solution is still really elegant though. You could just regexing the string first without having to refactor the rest of the code.

The task was different until yesterday...

This solution does not satisfy the whitespace criteria of the kata:

The input string can have leading, trailing whitespaces and more than a unique whitespace between two consecutive numbers

Why is there a forward slash in the substring replacement parameter? I don't see any syntax for it in MDN documentation.

Goddamn, that's beautiful

Thats's a pretty dramatic difference in performance.