but it's a slow old process as you have to use Espruino as a USB-Serial bridge. You can read out the firmware first which gives you a good way of detecting if what you're doing is working without risking bricking anything :)
You could actually just use a separate USB-TTL converter and stick it into the correct holes in the ESP8266 and do it that way though?
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.
It's a shame the v40 firmware doesn't support it. I believe that is the firmware built into all Espruino WiFi boards.
You should be able to update the firmware using the code at http://www.espruino.com/ESP8266#use-espruino
(The pins you need are in https://github.com/espruino/EspruinoDocs/blob/master/devices/EspruinoWiFi.js#L1)
but it's a slow old process as you have to use Espruino as a USB-Serial bridge. You can read out the firmware first which gives you a good way of detecting if what you're doing is working without risking bricking anything :)
You could actually just use a separate USB-TTL converter and stick it into the correct holes in the ESP8266 and do it that way though?