Would it keep my battery better to charge my iPhone on or off overnight?

Would it keep my battery better to charge my iPhone on or off overnight?

You shouldn't charge it overnight either way.It'll drain the battery. Trust me.

Don't charge overnight, it over charges the battery and ruins it, that's why my last phone got ruined, but on is better

You can charge the battery with the iPhone off or on. The battery will charge more slowly if the iPhone is on, since in that case the charger is providing power both for the phone and to charge the battery, but that's the only difference.

Leaving the phone (off or on, doesn't matter) charging overnight is not a problem. The charging circuits will automatically stop charging when the battery is fully charged. You can disconnect the charger when the battery is fully charged if you like, but it makes no difference.

You will hear from people who say things like "I left my phone on charging overnight and it killed the battery." But this is the _post hoc_ fallacy. Batteries fail all the time, and the fact that a battery failed while being charged in a certain way doesn't mean the charging method killed the battery. It's just coincidence.

Really… If you did continue full charging current into a Lithium-polymer battery (which is what iPhone and almost all other modern phones use) for hours after it was fully charged, the battery would probably burst and maybe catch fire. That didn't happen to your battery, right? Then the problem was not due to leaving the battery "on charge" all night. It isn't really left on charge!