JSFiddle - React, Tailwind, and code Playground

JavaScript

var url = 'https://github.com/settings/profile';
var req = new Request(url, { credentials: 'include', mode: 'no-cors'});
fetch(req).then(
  function(response) {
    // first byte of `response` received!
    T1 = performance.now();
    console.log('T1=' + T1);
  }
);
setInterval(function() {
  var entries = performance.getEntries();
  //console.log(entries);
  var lastEntry = entries[entries.length - 1];
  if (lastEntry.name == url) {
    T2minT1 = lastEntry.responseEnd - T1;
    console.log('T2minT1=' + T2minT1);
  }
}, 1);