Getting started with Espruino, a JavaScript interpreter for microcontrollers: 
If you’ve used microcontrollers like the Arduino before, you might be used to pushing compiled code onto the device and then just hoping it does what it’s supposed to. The chip is literally a black box: If you don’t add print statements (or they don’t get a chance to execute), you’ll have no idea what your code is doing (or even if it’s doing anything at all).
read more
Opensource.com – gfwilliams
Supporting Open Source.