Building an array of checked checkboxes

I am building a screen where I need to verify if any changes were made
when the user tries to leave the screen. I have list of checkboxes where
codes are selected. I am trying to compare those to a copied set in a
non-displayed DIV. I am using prototypeJS for most of my javascript, but
I am new to both javascript and prototypeJS. Trying to self teach, but I
am not big fan of the prototypeJS documentation.

Here is what I am trying

My checkbox ID's are savecode and code. All boxes in each group have the
same id.

newcode = $$('#code:checked');
savedcode = $$('#savecode:checked');

if (savecode != newcode) {

do something here;

}

This always says the are not equal. I think more than the input value is
being pulled into my variables.