How to make a web app for your own Bluetooth Low Energy device? Step 5

main.js

// Selected device object cache
let deviceCache = null;

// Launch Bluetooth device chooser and connect to the selected
function connect() {
  return (deviceCache ? Promise.resolve(deviceCache) :
      requestBluetoothDevice()).
      then(device => connectDeviceAndCacheCharacteristic(device)).
      then(characteristic => startNotifications(characteristic)).
      catch(error => log(error));
}

function requestBluetoothDevice() {
  //
}

// Connect to the device specified, get service and characteristic
function connectDeviceAndCacheCharacteristic(device) {
  //
}

// Enable the characteristic changes notification
function startNotifications(characteristic) {
  //
}

// Output to terminal
function log(data, type = '') {
  //
}