Monome.js is a thin wrapper around libmonome.
Here's a quick example how to get started (in CoffeeScript).
{Monome} = require 'monome'
monome = new Monome '/dev/tty.usbserial-m64-0123'
monome.onButtonDown = ({x, y}) ->
monome.setLED x, y, on
monome.onButtonUp = ({x, y}) ->
monome.setLED x, y, off
monome.start()'