Puck.js Connect to Adafruit Feather Board

Ahh - ok. Right, well, first off to detect the feather, using MAC address is great if it's just one-off. You can see it reports as:

  BluetoothDevice: {
    "id": "ff:8d:05:ae:17:64 random",
    "rssi": -45,
    "data": new Uint8Array([2, 1, 6, 2, 10, 0, 17, 6, 158, 202, 220, 36, 14, 229, 169, 224, 147, 243, 163, 181, 1, 0, 64, 110]).buffer,
    "services": [
      "6e400001-b5a3-f393-e0a9-e50e24dcca9e"
     ]
   },

So you can do:

NRF.requestDevice({ filters: [{ services: ['6e400001-b5a3-f393-e0a9-e50e24dcca9e"'] }] }).then(function(device) { ... });

To return any device advertising the Nordic UART service.

What you're doing with Serial1.* is you're using the physical UART on the Puck on pins D28/29 - that's nothing to do with Bluetooth. What you need is https://www.espruino.com/BLE+UART

So your code would be more like:

// Function to send a message
function sendMessage(message) {
  NRF.connect("ff:8d:05:ae:17:64 random").then(function(d)   {
    device = d;
    console.log("Device ",device);
    require("ble_simple_uart").write(device, message, function() {
      print('Done!');
    });
  });
}
// Send a message when the button is pressed
setWatch(function() {
  sendMessage("Hello, Arduino!");
}, BTN, { edge: "rising", debounce: 50, repeat: true });