Detecting country using Cloudflare Workers

country-detector.js

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

const countries = {
  US: "USA",
  CA: "CAN",
  FR: "FRA",
  DE: "DEU",
  NL: "NLD",
  IT: "ITA",
  PT: "PRT",
  IE: "IRL",
  GB: "GBR",
  AU: "AUS",
  NZ: "NZL",
  JP: "JPN",
  SG: "SGP",
  AE: "ARE",
  CH: "CHE",
  IN: "IND"
}

async function handleRequest(request) {
  let countryCode;
  // Sometimes cf object is not present and in that case, we default to the USA
  if (!request.cf || !request.cf.country) countryCode = JSON.stringify({ country_code_iso3: "USA" });
  else {
    countryCode = request.cf.country;
    // The app expects ISO3 country codes which exists in the `countries` object
    if (countries[countryCode]) countryCode = JSON.stringify({ country_code_iso3: countries[countryCode] })
    // Again, defaulting to the USA if someone is from a country that's not supported
    else countryCode = JSON.stringify({ country_code_iso3: "USA" });
  }

  let response = new Response(countryCode, {
    headers: {
      "content-type": "application/json;charset=UTF-8",
      "Access-Control-Allow-Origin": "*",
    }
  });

  return response;
}