With the flash module you need to be a bit more careful as you can damage the interpreter - however I have tried to restrict access so that you can't destroy the bootloader and 'brick' your Puck
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.
As @MaBe says you can just use that module - or you can go lower-level and use the flash module: http://www.espruino.com/Reference#Flash
With the flash module you need to be a bit more careful as you can damage the interpreter - however I have tried to restrict access so that you can't destroy the bootloader and 'brick' your Puck