performance.js

function getNavTiming(name) {
  if (!window.performance || !window.performance.timing) return 'unsupported';
  var t = window.performance.timing;
  var startName = name + 'Start', endName = name + 'End';
  if (name.indexOf('dom') == 0 && name.indexOf('domain') == -1) {
    startName = 'responseStart'; endName = name;
  }
  switch (name) {
    case 'load': startName = 'responseStart'; endName = 'loadEventEnd'; break;
    case 'connect':
      if (t.secureConnectionStart > 0) endName = 'secureConnectionStart';
      break;
    case 'secureConnection': endName = 'connectEnd'; break;
    case 'request': endName = 'responseStart'; break;
  }
  if (!(startName in t) || !(endName in t)) return 'invalid';
  if (t[startName] == 0 || t[endName] == 0) return 'n/a';
  var delta = t[endName] - t[startName], total = t[endName] - t.navigationStart;
  return delta + 'ms. Total: ' + total + 'ms';
}