Chromatic step sequencer

I have a question - how difficult it is to write JS midi plug-in? It is about the simplest step-sequencer. The essence of this - give the input MIDI note sequencer and gives the chromatic scale (up to 16 or 32 steps) of this note to a specific MIDI channel. Not need beat-sync,start-stop sync, for live playing only. Management : 1 - key note 2 - steps (1-16) 3 - out midi channel 4 - manual reset on first step somebody help me?

Please someone, write a plugin! I want to play only one note (Drum trigger) to midi output to a chromatic scale. and the ability to automate the back button on the first note. number of steps - from 1 to 16 ..

already done, included in reaper: babysequencer