This is the code behind the https://geolocation-json.joe.workers.dev/ cloudflare worker

index.js

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

function getUrlVars(url) {
    var vars = {};
    var parts = url.replace(/[?&]+([^=&]+)=([^&]*)/gi, function(m,key,value) {
        vars[key] = value;
    });
    return vars;
}

async function handleRequest(request) {
  // Is it a get request?
  if(request.method == 'GET'){
    // Set the latitude
    if(typeof getUrlVars(request.url)["latitude"] !== 'undefined'){
      latitude = getUrlVars(request.url)["latitude"];
    }
    else{
      latitude = request.cf.latitude;
    }
    // Set the longitude
    if(typeof getUrlVars(request.url)["longitude"] !== 'undefined'){
      longitude = getUrlVars(request.url)["longitude"];
    }
    else{
      longitude = request.cf.longitude;
    }
  }else{
    latitude = request.cf.latitude;
    longitude = request.cf.longitude;
  }

  // API Crap
  let endpoint = "https://www.mapquestapi.com/geocoding/v1/reverse?key={ MAPQUEST API KEY GOES HERE }&location="+latitude+"%2C"+longitude+"&outFormat=json&thumbMaps=false";

  const init = {
    headers: {
      "content-type": "application/json;charset=UTF-8",
    },
  }

  const response = await fetch(endpoint,init)
  const mqContent = await response.json()

  // The struct that holds the details of who the user is
  let user = {
    latitude:latitude,
    longitude:longitude,
    cfCountry:request.cf.country,
    cfCity:request.cf.city,
    cfLatitude:request.cf.latitude,
    cfLongitude:request.cf.longitude,
    cfPostalcode:request.cf.postalCode,
    cfRegion:request.cf.region,
    cfRegioncode:request.cf.regionCode,
    cfTimezone:request.cf.timezone,
    mqStreet:mqContent.results[0].locations[0].street,
    mqCity:mqContent.results[0].locations[0].adminArea5,
    mqState:mqContent.results[0].locations[0].adminArea3,
    mqZip:mqContent.results[0].locations[0].postalCode
  }

  return new Response(JSON.stringify(user, null, 2), {
      headers: {
        "content-type": "application/json;charset=UTF-8"
      }
    })
}