How To: Get 'screen' [x, y] location of an element.

How To: Get 'screen' [x, y] location of an element.

Some element in the doc, say #button, what is it's absolute 'screen' location?
I know how to calculate it in plain JS but am new to jQuery. 
...and yes, I have looked in the API doc but with no luck.

Anyone? ...thanks

Greg