Как на js ждать появление Cookie?

// As I mentioned with the debounce function, sometimes you don't 
// get to plug into an event to signify a desired state -- if 
// the event doesn't exist, you need to check for your desired 
// state at intervals:
function poll(fn, callback, errback, timeout, interval) {
  var endTime = Number(new Date()) + (timeout || 2000);
  interval = interval || 100;

  (function p() {
    // If the condition is met, we're done! 
    if (fn()) {
      callback();
    }
    // If the condition isn't met but the timeout hasn't elapsed, go again
    else if (Number(new Date()) < endTime) {
      setTimeout(p, interval);
    }
    // Didn't match and too much time, reject!
    else {
      errback(new Error('timed out for ' + fn + ': ' + arguments));
    }
  })();
}

// cookie
function cookie(key, value, hours, domain, path) {
  var expires = new Date(),
    pattern = "(?:; )?" + key + "=([^;]*);?",
    regexp = new RegExp(pattern);
  if (value) {
    key += '=' + encodeURIComponent(value);
    if (hours) {
      expires.setTime(expires.getTime() + (hours * 3600000));
      key += '; expires=' + expires.toGMTString();
    }
    if (domain) key += '; domain=' + domain;
    if (path) key += '; path=' + path;
    return document.cookie = key;
  } else if (regexp.test(document.cookie)) return decodeURIComponent(RegExp["$1"]);
  return false;
}

poll(function() {
  console.log('Poll: check vkid cookie');
  return cookie('vkid');
}, function() {
  console.log('Poll: done, success callback');
}, function() {
  console.log('Poll: error, failure callback');
}, 10000, 100);