In addition to the links provided by JumJum, I have found the following to be exceptionally useful while building custom extensions for Espruino on the ESP32.
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.
@DavidM
In addition to the links provided by JumJum, I have found the following to be exceptionally useful while building custom extensions for Espruino on the ESP32.
Compiling:
https://github.com/espruino/Espruino/blob/master/README_Building.md
JSON Extension Format:
https://github.com/espruino/Espruino/blob/master/scripts/common.py#L52
Espruino Internals:
http://forum.espruino.com/conversations/357006/#comment15666995
http://forum.espruino.com/conversations/302250/
http://www.espruino.com/Internals