Identify users visited websites by HTML5 Resource Timing API

<script>
/* The scripts purpose is to identify internal traffic but it might be used to verify if a user has visited a certain website.
* By assuming a user visited website A, resources or connection information like DNS or SSL get's cached.
* Leveraging the HTML5 Resource Timing API (https://www.w3.org/TR/resource-timing/) a known resources get's attached to the DOM.
* If the resource or it's connection information was already cached the following metrics should be zero:
* domainLookupStart, domainLookupEnd, connectStart, connectEnd, requestStart, responseStart
*
* This script is extended with Google Tag Manager events to track the findings. Later I will elaborate to implement the userID.
*/

  var imageCheck = document.createElement("img");
  imageCheck.src = "YOUR-FULL-RESOURCE-PATH";
  imageCheck.style = "display: block; visibility: hidden;";
  imageCheck.id = "imageCheck";
  document.body.appendChild(imageCheck);

  document.getElementById("imageCheck").addEventListener("load", function() {
    console.log("Resource loaded");
    console.log(document.getElementById("imageCheck"));
    console.log("Resources complete: " + document.getElementById("imageCheck").complete);
    console.log("Natural width: " + document.getElementById("imageCheck").naturalWidth);

    var resourceList = !(/MSIE (\d.\d+);/.test(navigator.userAgent) || window.performance.getEntriesByType == undefined) ? window.performance.getEntriesByType("resource") : "undefined",
    resuorceUrl = document.getElementById("imageCheck").src,
    found = resourceList.filter(function(item) { return item.name === resuorceUrl; }),
    foundTiming = [
      found[0].domainLookupEnd - found[0].domainLookupStart,
      found[0].connectEnd - found[0].connectStart,
      found[0].requestStart,
      found[0].responseStart
    ];

    console.log("domainLookupStart: " + found[0].domainLookupStart);
    console.log("domainLookupEnd: " + found[0].domainLookupEnd);

    console.log("connectStart: " + found[0].connectStart);
    console.log("connectEnd: " + found[0].connectEnd);

    console.log("requestStart: " + found[0].requestStart);
    console.log("responseStart: " + found[0].responseStart);

    if(found[0].name.indexOf("https") !== -1) {
      console.log("secureConnectionStart: " + found[0].secureConnectionStart);
      foundTiming[foundTiming.length] = found[0].secureConnectionStart;
    }

    if (foundTiming.join("|").indexOf("0") !== -1) {
      //console.log("Zero's baby: " + foundTiming.reduce((a, b) => a + b, 0) === 0);
      console.log("foundTiming: " + foundTiming.join("|"));
      dataLayer.push ({ 'event': 'internalTraffic', 'eventCategory': 'Internal traffic', 'eventAction': foundTiming.join("|"), 'eventLabel': undefined, 'eventValue': undefined, 'nonInteractive': 1});
    } else {
      //console.log("Zeor's baby: " + foundTiming.reduce((a, b) => a + b, 0) === 0);
      console.log("foundTiming: " + foundTiming.join("|"));
      dataLayer.push ({ 'event': 'internalTraffic', 'eventCategory': 'External traffic', 'eventAction': foundTiming.join("|"), 'eventLabel': undefined, 'eventValue': undefined, 'nonInteractive': 1});
    }
  }, false);
  document.getElementById("imageCheck").addEventListener("error", function() {
    console.log("Resource didn't load");
    dataLayer.push ({ 'event': 'internalTraffic', 'eventCategory': 'Resource not found', 'eventAction': undefined, 'eventLabel': undefined, 'eventValue': undefined, 'nonInteractive': 1});
  }, false);
</script>