Get the ID / class of the part of the form that has been repainted with an AJAX callback? I have an AJAX form with a callback that fires some JavaScript when the form is submitted. 

I need to know what has been repainted. Can I get the class / ID of the parts of the form that have been changed by submitting the form? 

AJAX callback:

function _my-module_form_process_callback_js($form, &amp;$form_state) {
  $commands = array();

  $commands[] = array (
    'command' =&gt; 'customSomething',
  );


JavaScript: 

  Drupal.ajax.prototype.commands.customSomething = function(ajax, response, status) {

    console.log(ajax);

  };


By logging ajax I can see the form ID and class. However I don't belive that the entire form is being repainted. Most of the form is unchanged, its only one fieldset that changes.
I don't know if its the best solution but this works: 

  Drupal.ajax.prototype.commands.customSomething = function(form) {

    var formId = '#' + form.form.context.id;

  };