resource timing

function getStats() {
  var domainStats = {};
  let resourcesOnPage = {};
  document.querySelectorAll("SCRIPT, LINK").forEach((r) => {
     let src = r.src;
     if (r.rel === "preload" || r.rel === "stylesheet") { 
       src = r.href;
     } 
     if (src) {
       if (src[0] === "//") {
         src = window.location.protocol + "//" + window.location.hostname + src;
       }
       resourcesOnPage[src] = true;
      }
   });
     
  performance.getEntriesByType("resource").forEach((r) => {
     
     if (!resourcesOnPage[r.name]) {
       return;
     }
     
     resourcesOnPage[r.name] = "found";

     let duration =  r.responseEnd ?  r.responseEnd - r.startTime : -1; 
     let url = new URL(r.name);
     let stats = domainStats[url.host]
     if (!stats) {
        stats = {count: 1, min: duration, max: duration, total: duration, latest: r.responseEnd, failed: duration == -1 ? 1 : 0};
     } else {
        stats.count += 1;
        if (r.responseEnd > stats.responseEnd) {
          stats.responseEnd = r.responseEnd;
        }
        if (duration == -1) {
          stats.failed += 1;
        } else {
          if (duration < stats.min || stats.min === -1) { stats.min = duration };
          if (duration > stats.max) { stats.max = duration };
         }
        stats.total += duration;
     }
     domainStats[url.host] = stats;
  });
  
  var failed = [];
  Object.keys(resourcesOnPage).forEach((k) => {
    if (resourcesOnPage[k] !== "found") {
      failed.push(resourcesOnPage[k]);
    }
  });
  
  if (failed.length) {
     domain["failed"] = failed;
  }
  
  return domainStats;
}