Is it bad to overcharge my iPhone 4S?

My friend keeps bugging me that if I overcharge my iPhone, then it will just completely destroy the battery. I think that isn't true. So is it bad to leave it charging overnight, and use it all the time while it's charging?

Naah.

Not really, just don't charge it for like days on end. I charge my iphone over night and the batteries is fine. I sometimes use it while it's charging too! Nothing has happened to it…
I have had this iphone for about 1 year and 7 months

No. Its programed to not overcharge.

You can't overcharge an iPhone.