Thumb opcodes here: https://ece.uwaterloo.ca/~ece222/ARM/ARM7-TDMI-manual-pt3.pdf - it should be pretty easy to make an assembler from that...
@Gordon started
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.
Thumb opcodes here: https://ece.uwaterloo.ca/~ece222/ARM/ARM7-TDMI-manual-pt3.pdf - it should be pretty easy to make an assembler from that...