Cloudflare worker to send statistics to Matomo

cloudflare-matomo-worker.js

async function trackVisit (request, visitorId) {
  let data = {
    token_auth: 'secret',
    country: request.headers.get('CF-IPCountry'),
    urlref: request.referrer || request.headers.get('Referer'),
    idsite: 1,
    lang: request.headers.get('Accept-Language'),
    apiv: 1,
    rand: Math.random().toString(16).slice(2),
    url: request.url,
    _id: visitorId.slice(0, 16),
    rec: 1,
    ua: request.headers.get('User-Agent')
  }
  let url = 'https://logux.matomo.cloud/matomo.php?' + Object.entries(data)
    .map(([k, v]) => `${ k }=${ encodeURIComponent(v) }`)
    .join('&')
  await fetch(url)
}

function getVisitorId (...headers) {
  for (let header of headers) {
    if (typeof header === 'string') {
      let match = header.match(/__cfduid=([0-9a-f]+)(;|$)/)
      if (match) return match[1]
    }
  }
}

function shouldBeIgnored (request, response) {
  return request.headers.get('DNT') === '1' ||
         request.headers.get('From') === 'sw@logux.io' ||
         !(response.headers.get('Content-Type') || '').includes('text/html')
}

async function fetchAndTrack (event) {
  try {
    let response = await fetch(event.request)
    if (!shouldBeIgnored(event.request, response)) {
      let visitorId = getVisitorId(
        event.request.headers.get('Cookie'),
        response.headers.get('Set-Cookie')
      )
      event.waitUntil(trackVisit(event.request, visitorId))
    }
    return response
  } catch (err) {
    return new Response(err.stack || err)
  }
}

addEventListener('fetch', async event => {
  event.respondWith(fetchAndTrack(event))
})