Thank you for your kind reply, Gordon! :-)
I am a frontend web developer (that's why I love Espruino), but as I said I am a newbie in electronics, hence I am not sure to be able to do what you are suggesting.
I know I can control servos directly from Espruino (already successfully done!), but I am trying to learn something new reusing hardware from previous experiments with different microcontrollers.
By the way, I would like to try to "translate" Adafruit c++ code to a module for Espruino, avoiding to bother you with my personal experiments! ;-)
Could you please suggest me a way to start? Maybe the code of another module you already ported into js for Espruino?
I definitely wanna deepen this stuff. Maybe the libs/README.md file (https://github.com/espruino/Espruino/blob/master/libs/README.md) could be a starting point.