Ping a server with HEAD requests until it's up and then reload

reload.js

function reload(url, delay) {
  url = url || '/';
  delay = delay || 10;

  var req = new XMLHttpRequest();

  req.onload = window.location.reload.bind(window.location);
  req.onerror = setTimeout.bind(null, reload.bind(null, url, delay), delay);

  req.open('head', url, true);
  req.send();
}