Yes, very harmful to the overall battery capacity..
After 3-4 such nights you will see the difference..
better use ur pc for that
What are you talking about. Those battery problems are a thing of the past. Contrary to my and several other's experience( see the thread below), today's batteries have a way of protecting themselves and there is no harm in keeping phone plugged in overnight.
Is it safe to keep your GS3 on charger all night? - Android Forums at AndroidCentral.com.
One post in the above thread clarifies it all :
To the OP: Charge your device every night, if that's what pleases you. It's designed to last longest that way (i.e. will last you years instead of months) and will ensure that when you start your day, your device is topped off and ready to keep up with you. Studies I've read claim that a battery that is never allowed to drop below 50% will last 3 times longer over the years than a battery that is regularly drained to 0. Obviously it's not -bad- to let it drop to 0. It's just better to keep it from doing so. (Note, this is only true of the newer Li-Ion batterys found in cell phones. Older Ni-Cad batterys had that memory problem that is so infamous. Cell phone batteries do not)