ibeacon.js

navigator.mozBluetooth.defaultAdapter.startLeScan([]).then(handle => {
  console.log('Start scanning', handle);
  handle.ondevicefound = e=> {
    var record = parseScanRecord(e.scanRecord);
    if (record) {
      console.log('Found an iBeacon', record.uuid, record.major, record.minor, e.rssi);
    }
  }
 
  setTimeout(() => {
    console.log('Stop scanning');
    navigator.mozBluetooth.defaultAdapter.stopLeScan(handle)
  }, 5000);

}, err => console.error(err))

function parseScanRecord(scanRecord) {
  var view = new Uint8Array(scanRecord);
  
  // Company ID does not have fixed length, so find out where to start by
  // finding 0x02, 0x15 in byes 4..8
  for (var start = 4; start < 8; start++) {
    if (view[start] === 0x02 && view[start + 1] === 0x15) {
      break;
    }
  }
  
  if (start === 8) {
    return;
  }
  
  // Now UUID is the next 16 bytes right after 0x15
  start += 2;
  var uuid = bytesToHex(view.slice(start, start + 16));
  
  // major / minor are two bytes each
  start += 16;
  var major = (view[start] & 0xff) * 0x100 + (view[start + 1] & 0xff);

  start += 2;
  var minor = (view[start] & 0xff) * 0x100 + (view[start + 1] & 0xff);
  
  return { uuid: uuid, major: major, minor: minor };
}

var hexArray = '0123456789ABCDEF'.split('');
function bytesToHex(bytes) {
  var hex = [];
  for (var j = 0; j < bytes.length; j++) {
    var v = bytes[j] & 0xff;
    hex[j * 2] = hexArray[v >>> 4];
    hex[j * 2 + 1] = hexArray[v & 0x0f];
  }
  return hex.join('');
}