Web Bluetooth / Read Descriptors Sample

function onButtonClick() {   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 any Bluetooth Device...');   navigator.bluetooth.requestDevice({   // filters: [...] <- Prefer filters to save energy & show relevant devices.       acceptAllDevices: true,       optionalServices: [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 => {     log('Getting Descriptors...');     return characteristic.getDescriptors();   })   .then(descriptors => {     let queue = Promise.resolve();     descriptors.forEach(descriptor => {       switch (descriptor.uuid) {          case BluetoothUUID.getDescriptor('gatt.client_characteristic_configuration'):           queue = queue.then(_ => descriptor.readValue()).then(value => {             log('> Client Characteristic Configuration:');             let notificationsBit = value.getUint8(0) & 0b01;             log('  > Notifications: ' + (notificationsBit ? 'ON' : 'OFF'));             let indicationsBit = value.getUint8(0) & 0b10;             log('  > Indications: ' + (indicationsBit ? 'ON' : 'OFF'));           });           break;          case BluetoothUUID.getDescriptor('gatt.characteristic_user_description'):           queue = queue.then(_ => descriptor.readValue()).then(value => {             let decoder = new TextDecoder('utf-8');             log('> Characteristic User Description: ' + decoder.decode(value));           });           break;          case BluetoothUUID.getDescriptor('report_reference'):           queue = queue.then(_ => descriptor.readValue()).then(value => {             log('> Report Reference:');             log('  > Report ID: ' + value.getUint8(0));             log('  > Report Type: ' + getReportType(value));           });           break;          default: log('> Unknown Descriptor: ' + descriptor.uuid);       }     });     return queue;   })   .catch(error => {     log('Argh! ' + error);   }); }  /* Utils */  const valueToReportType = {   1: 'Input Report',   2: 'Output Report',   3: 'Feature Report' };  function getReportType(value) {   let v = value.getUint8(1);   return v + (v in valueToReportType ?       ' (' + valueToReportType[v] + ')' : 'Unknown'); }