ajax-responder.js

//fetches all JS src and concats them
// md5() the above
// On click / form submit add ID from above

ajax_render

$js_page_id = $_POST['js_page_id'];
$files_in_parent = cache_get($js_page_id, 'cache');

preprocess_page

hook_preprocess_page() {
  foreach (drupal_add_js() as $type => $data) {
    if ($type == 'file') {
      foreach $data as $path => $info {
        $paths .= base_path() . $path;
        $js_files[] = $info;
      }
    }
  }

  $js_page_id = md5($paths);
  cache_set($js_page_id, $js_files);
}