So you could get your code, run it through that command-line tool, and then use whatever you've got connected to the RX/TX pins to send the bytes from that file - and you've got your firmware update sorted.
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.
Just to add - with https://github.com/espruino/EspruinoToolÂs you can output what would have been written to espruino with
-o out.js
So you could get your code, run it through that command-line tool, and then use whatever you've got connected to the RX/TX pins to send the bytes from that file - and you've got your firmware update sorted.