Yes if you are hired as a contractor. You are the author of the written code and you own the copyright. You lose the copyright to the hiring party only if the "work-for-hire" clause is in the signed contract.
And in turn the company should look to copyright assignment.
As a contractor, you shouldn't be signing umbrella work-for-hire clauses either. They're usually part of the shotgun approach of "we own everything you do, always, ever".
Copyright assignment is where the give-and-take should take place (which I'm surprised the author didn't speak about) - "company gets copyright assignment based on XYZ (which could include payment, equity agreement, etc.)"
IANAL - I just hire one with one who protects me from signing stupid stuff and is occasionally the nasty stick when clients act up.
