@ankr The problem is, .toString() is basically the same as .join(","). So you end up adding a load of commas you don't need, and then removing them. A simple .join("") would do the same with less work (as shown in the solution).

I guess the essentials are the same - although you could skip the i flag in your regex.

Excelente, best practice. I like codewars :D

My past solution, after the method sort(), pass the type Object toString() and replace with regex.
//code.split('').sort().toString().replace(/,/gi,'');