isPopupBlocked.js

var isPopupBlocked = function() {
  var isBlocked,
      popup = window.open('about:blank', 'popup_test','width=5, height=5, left=0, top=0');

  // pop under
  if(popup) popup.blur();
  window.focus();

  isBlocked = !popup || typeof popup == 'undefined' || typeof popup.closed=='undefined' || popup.closed || popup.innerHeight == 0; 
  if(popup) popup.close();

  return isBlocked;
};