Using an PCF8575 Expander as a Virtual Board (SparkFun I2C Expander Breakout - PCF8575)
Breadboard for "Expander - PCF8575"

Fritzing diagram: expander-PCF8575.fzz
Run this example from the command line with:
node eg/expander-PCF8575.js
const { Board, Expander, Leds } = require("johnny-five");
const board = new Board();
board.on("ready", () => {
  const virtual = new Board.Virtual(
    new Expander("PCF8575")
  );
  const leds = new Leds(
    Array.from(Array(8), (_, pin) =>
      ({ pin, board: virtual })
    )
  );
  leds.blink(500);
  board.repl.inject({
    leds
  });
});