Leaving a desktop computer plugged in all the time is normal and what they're built for and I would never unplug my desktop computer unless there was a risk of a lightning storm that could strike and damage my computer.
As for a laptop computer those are safe to leave plugged in all the time as well and the battery will automatically stop charging once it's fully charged.
I also leave my laptop plugged in all the time and when I'm at home near an electrical outlet and only use the battery in the laptop when outside or away from home.