Is it safe to attach battery when the laptop is plugged in and being used?

Let say initially I removed my laptop battery because it's already fully charged. Then I plug in my laptop to the wall socket, and then use my laptop. After that, I need to go somewhere, but I don't want to shut down my laptop, attach the battery, and then power it on again. So I attach my battery without shutting down the laptop. Is this safe? Or will it damage either the laptop or the battery or both?