Why code's answer is 13?

Question

var I= 12;
(++I) % 3;
alert(I);

Answer 1

Pikachu ~ swim ~
i see i see. Thanks for explanation. :D

*hugs*

Answer 2

++l makes the variable increase by one, and when you %3, it actually has no effect because you are not defining anything with it.
Because 12 is the original variable and it increases by one, the answer will be 13.