proto.js

  function toHexString(byteArray) {
    return Array.from(byteArray, function(byte) {
      return ('0' + (byte & 0xFF).toString(16)).slice(-2);
    }).join('')
  }

  var parseRawRuuvi = function(manufacturerDataString){

    let robject = {};
    let data = manufacturerDataString;
    let dataFormat = data[0] & 0xFF;
    let temperature = (data[1] << 8 | data[2] & 0xFF);
    if (temperature > 32767) {
      temperature -= 65535;
    }
    temperature /= 200.0;
    let humidity =  ((data[3] & 0xFF) << 8 | data[4] & 0xFF) / 400.0;
    let pressure = ((data[5] & 0xFF) << 8 | data[6] & 0xFF) + 50000;
    let accelerationX = (data[7] << 8 | data[8] & 0xFF) / 1000.0;
    let accelerationY = (data[9] << 8 | data[10] & 0xFF) / 1000.0;
    let accelerationZ = (data[11] << 8 | data[12] & 0xFF) / 1000.0;
    let powerInfo = (data[13] & 0xFF) << 8 | data[14] & 0xFF;
    let batteryVoltage = (powerInfo >>> 5) / 1000.0 + 1.6;
    let txPower = (powerInfo & 0b11111) * 2 - 40;
    let movementCounter = data[15] & 0xFF;
    let measurementSequenceNumber = (data[16] & 0xFF) << 8 | data[17] & 0xFF;
    // let mac = toHexString(data.subarray(18));

    robject.destination_endpoint = dataFormat;
    robject.temperature = temperature;
    robject.humidity = humidity;
    robject.pressure = pressure;
    robject.accelerationX = accelerationX;
    robject.accelerationY = accelerationY;
    robject.accelerationZ = accelerationZ;
    robject.batteryVoltage = batteryVoltage;
    robject.txPower = txPower;
    robject.movementCounter = movementCounter;
    robject.measurementSequenceNumber = measurementSequenceNumber;
    // robject.mac = mac;

    return robject;
  }



navigator.bluetooth.requestLEScan(
        {acceptAllAdvertisements: true, keepRepeatedDevices: true}
).then(() => {
  navigator.bluetooth.addEventListener('advertisementreceived', event => {
  let value = event.manufacturerData.get(0x0499);
  if (!value) {
    return;
  }
  let dataFormat = value.getUint8(0);
  if (dataFormat != 5) {
    return;
  }
  let a = [];
  for (let i = 0; i < value.byteLength; i++) {
    a.push('0x' + ('00' + value.getUint8(i).toString(16)).slice(-2));
  }
  console.log(a.join(' '));
  console.log(parseRawRuuvi(a));

  });
})