Determine whether there is an ajax request in progress managed by Drupal.ajax

ajaxInProgress.js

(function(){

// Determine if any ajax call is currently in progress.
Drupal.ajaxInProgress = function() {
  for (var id in Drupal.ajax) {
    if (Drupal.ajax[id].ajaxing === true) {
      return true;
    }
  }
  return false;
};

})();