var myCharacteristic;

function onStartButtonClick() {
  let serviceUuid = document.querySelector('#service').value;
  if (serviceUuid.startsWith('0x')) {
    serviceUuid = parseInt(serviceUuid);
  }

  let characteristicUuid = document.querySelector('#characteristic').value;
  if (characteristicUuid.startsWith('0x')) {
    characteristicUuid = parseInt(characteristicUuid);
  }

  log('Requesting Bluetooth Device...');
  navigator.bluetooth.requestDevice({filters: [{services: [serviceUuid]}]})
  .then(device => {
    log('Connecting to GATT Server...');
    return device.gatt.connect();
  })
  .then(server => {
    log('Getting Service...');
    return server.getPrimaryService(serviceUuid);
  })
  .then(service => {
    log('Getting Characteristic...');
    return service.getCharacteristic(characteristicUuid);
  })
  .then(characteristic => {
    myCharacteristic = characteristic;
    return myCharacteristic.startNotifications().then(_ => {
      log('> Notifications started');
      myCharacteristic.addEventListener('characteristicvaluechanged',
        handleNotifications);
    });
  })
  .catch(error => {
    log('Argh! ' + error);
  });
}

function onStopButtonClick() {
  if (myCharacteristic) {
    myCharacteristic.stopNotifications().then(_ => {
      log('> Notifications stopped');
      myCharacteristic.removeEventListener('characteristicvaluechanged',
        handleNotifications);
    });
  }
}

function handleNotifications(event) {
  let value = event.target.value;
  let a = [];
  // Convert raw data bytes to hex values just for the sake of showing something.
  // In the "real" world, you'd use data.getUint8, data.getUint16 or even
  // TextDecoder to process raw data bytes.
  for (let i = 0; i < value.byteLength; i++) {
    a.push('0x' + ('00' + value.getUint8(i).toString(16)).slice(-2));
  }
  log('> ' + a.join(' '));
}

@@ -1244,32 +1244,37 @@
 pNotifications()
+%0A    
 .then(_ =%3E %7B%0A   
@@ -1403,32 +1403,90 @@
 Notifications);%0A
+    %7D)%0A    .catch(error =%3E %7B%0A      log('Argh! ' + error);%0A
     %7D);%0A  %7D%0A%7D%0A%0Af

add cacth when stopping notifications (#382)