split string in two on given index and return both parts

Question

I have a string that I need to split on a given index and then return both parts, seperated by a comma. For example:

string: 8211 = 8,211
        98700 = 98,         


        

Answer 1

If code elegance ranks higher than the performance hit of regex, then

'1234567'.match(/^(.*)(.{3})/).slice(1).join(',')
=> "1234,567"

There's a lot of room to further modify the regex to be more precise.

If join() doesn't work then you might need to use map with a closure, at which point the other answers here may be less bytes and line noise.