As far as ground loops - the ground that comes out of a mains power supply should be (at least partially) isolated from earth/mains neutral, so connecting them together shouldn't be a problem.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Great - glad it's working!
As far as ground loops - the ground that comes out of a mains power supply should be (at least partially) isolated from earth/mains neutral, so connecting them together shouldn't be a problem.