Control a Raspberry Pi Sense HAT LED Display
Work in progress. Your mileage may vary.
The state of affairs in Dec 2015 offers the following alternatives.
First, there’s the original library supported by the Raspberry team (https://github.com/RPi-Distro/python-sense-hat). Use this one for best user experience. One feature is that it is written in Python. This is a drawback if you want to be plain Javascript.
A Javascript wrapper for RTIMULib2 (https://github.com/rupnikj/nodeimu). It does supports gravity, air pressure, humidity and temperature, but not the matrix LED.
From https://github.com/teuteuguy/raspberry-sensor-sense-hat. Supports the matrix LED, but only via embedded python shell script escapes.