The simplest possible "virtual" Matter device. This is a nodejs script which runs on an actual computer and acts as a device that a reasonably modern Alexa (Amazon Echo) can pair with and send commands to. At time of writing, it can only be a light or a socket (that is: all you can tell it to do is turn on and off) but it doesn't need to run on any special hardware or a microcontroller; this is a device that can run on your laptop or whatever, for experimenting with. All connections to the device are local, on your LAN; you do not need to write an Alexa skill, and you do not need to expose the device to the internet. You do have to connect the device to the network yourself (which is fine if you're on a laptop); Matter has lots of clever ways to get a device onto your network if it isn't already, and this project deals with none of them.
This is a very basic redo of https://github.com/project-chip/matter.js/blob/main/packages/matter-node.js-examples/src/examples/DeviceNode.ts but in JS, not TypeScript, and with all the values hardcoded rather than settable from the command line.