See quick start guide on how to build and flash the firmware. Below is an example session:

mos build --arch ARCH        # Build the firmware. ARCH: esp8266, esp32, cc3200, stm32
mos flash                    # Flash the firmware
mos console                  # Attach a serial console and see device logs

See https://github.com/cesanta/mjs for the MJS engine information.

In src/, some codes try to call cpp function and class method from mongoose-os/mos/mjs.