The index of the first character is 0 and an email must have a local part so that means the index of "@" has to be at least 1. My guess is OP also forgot the index of the first character is 0 instead of 1 resulting in 1+1=2 (that or they meant >=).

Off by one errors are about half of working with arrays.

Yeah...I have an email address I use a lot, "me@(domain)". It's perfectly valid, despite indexOf("@") == 2.

Heh, I actually meant `>=`. But as others have pointed out, that still excludes 2 letter users. Really it should be `>= 0`.