Warper-oauth.js

// create popup window
var domain = 'http://wikimaps.mapwarper.net';
var myPopup = window.open(domain + '/u/auth/github?omniauth_window_type=newWindow&auth_origin_url=' + window.location.href, 'myWindow');

// periodical message sender
var messenger = setInterval(function() {
  var message = 'requestCredentials';
  //send the message and target URI
  myPopup.postMessage(message, domain);
}, 500);

// listen to response
window.addEventListener('message', function(event) {
  // the message listener get's triggered by any URL make sure it's the right one
  if (event.origin !== domain) return;
  clearInterval(messenger);
  console.log(event.data);
}, false);