cvazac

(function(w) {
  if (w != top) return

  var anchors = document.getElementsByTagName('a')
  w.addEventListener('load', checkVisibleAnchors)
  w.addEventListener('scroll', checkVisibleAnchors)

  var sum = 0, count = 0
  function checkVisibleAnchors() {
    sum -= performance.now()

cvazac

(function() {
  var tasks = []
  function run() {
    tasks.push(Array.prototype.slice.call(arguments))
    waitThenRun()
  }
  function waitThenRun() {
    requestAnimationFrame(function() {
      if (tasks.length === 0) {
        return

cvazac

;(function() {
  function getNatives(objects) {
    if (typeof objects === 'string') {
      objects = [objects]
    }

    var natives = {}
    if (objects.length) {
      var iframe = document.createElement('iframe')
      iframe.style.display = 'none'

cvazac

function isNativeFunction(fn) {
  return typeof fn === 'function' && fn.toString && !fn.hasOwnProperty('toString') &&
      /\[native code\]/.test(String(fn))
}
function checkNatives(fns) {
  var results = []
  for (var i = 0; i < fns.length; i++) {
    results[i] = {
      fn: fns[i],
      native: isNativeFunction(fns[i])

cvazac

(function() {
    if (window !== top) return;

    const bucketSize = 500, threshold = 30, stamps = []
    function measureFps() {
        const now = performance.now()
        if (stamps.length) {
            while (now - stamps[0] > bucketSize) {
                stamps.shift()
            }

cvazac

const query = `
CREATE TEMPORARY FUNCTION getHeaders(payload STRING)
RETURNS STRING
LANGUAGE js AS """
  try {
    var $ = JSON.parse(payload);
    var headers = $.response.headers;
    var st = headers.find(function(e) { 
      return e['name'].toLowerCase() === 'server-timing'
    });

cvazac

!(function() {
    const nativePO = window.PerformanceObserver
    const interfaces = {
      resource: 'PerformanceResourceTiming',
      longtask: 'PerformanceLongTaskTiming',
      // etc.
    }
    const polyfills = {
      longtask: LongTaskPolyFill
      // etc.

cvazac

!(function() {
    const nativePO = window.PerformanceObserver
    const polyfills = {
      longtask: LongTaskPolyFill
      // etc.
    }
    window.PerformanceObserver = (callback) => {
      let po, registeredPolyFills = []

      const observe = function(options) {

cvazac

function cachedInBrowser(resourceTimingEntry) {
  if (resourceTimingEntry.requestStart) {
    // has permissive Timing-Allow-Origin response header
    return resourceTimingEntry.transferSize === 0
  }

  // because.... physics?
  return resourceTimingEntry.duration < 30
}

cvazac

(function() {
  let userThinkTime = 0

  ;['alert', 'confirm', 'prompt'].forEach(function(methodName) {
    window[methodName] = (function(method) {
      return function () {
        userThinkTime -= performance.now()
        var returnValue = method.apply(window, arguments)
        userThinkTime += performance.now()
        return returnValue