It looks like on that board the IM0..IM3 wires (which define the mode) are hard-wired, so serial won't be an option and I guess you're stuck with the full 8 bits.
You might be able to use shiftOut to push the image data out quickly if you're lucky, but I'm not sure.
Honestly, it's going to be tricky, and the display will use up loads of your IO and be a pain to solder up. Personally I'd just buy a different SPI graphics display that is supported by Espruino :)
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 looks like on that board the IM0..IM3 wires (which define the mode) are hard-wired, so serial won't be an option and I guess you're stuck with the full 8 bits.
You'd need to copy the magic code from https://github.com/telamon/utft/blob/master/UTFT.cpp wherever S6D1121_8 is mentioned, and then use digitalWrite to implement LCD_Write_COM and LCD_Write_DATA.
You might be able to use shiftOut to push the image data out quickly if you're lucky, but I'm not sure.
Honestly, it's going to be tricky, and the display will use up loads of your IO and be a pain to solder up. Personally I'd just buy a different SPI graphics display that is supported by Espruino :)