To expand on this, the phone itself has a management system to make it so you can't overcharge your phone. Essentially current battery technology only has two points where your battery degrades more than it should, the first one is when it's fully charged, the other is when it's fully empty. Both are undesirable. This is why a 100% charge on your phone isn't actually a 100% battery charge, but slightly lower. This is also why your new tech always comes with a half full or more battery, because they charge it to about 80% in the factory, and accounting for natural degredation, it gives them enough of a charge to have on store shelves for years without compromising the battery, even with the device turned off.
It used to be the case that you needed to mind at what point you charged your phone, because it had a sort of memory that could degrade your battery life over time if you kept charging it at the same points, this hasn't been the case for a while, though.