Leaving a laptop plugged in does not typically damage the battery or present any danger to the device, but it can still wear the the battery over time.
Modern laptops use lithium-ion or lithium-polymer batteries, which are designed with built-in protections to prevent overcharging. Once the battery reaches 100% or the charge threshold, the laptop will stop charging and rely on AC power, to prevent damage.
Keeping Lithium batteries at full or low charge for extended periods can contribute to increased wear over time. For maximum battery life, it is recommended to set a charge threshold of ~80% within the laptops power settings and try to cycle the battery at-least once a month.
