(function($) {
  /**
   * Replaces this element with the specified content using a fade-out and
   * fade-in effect.
   *
   * @param {string} content
   *   The HTML to replace this element with.
   * @param {integer} fadeOutTime
   *   The number of milliseconds for the fade out (defaults to 400 msec).
   * @param {integer} fadeInTime
   *   The number of milliseconds for the fade in (defaults to 400 msec).
   */
  $.fn.fadeReplaceWith = function(content, fadeOutTime, fadeInTime) {
    if (fadeOutTime == null) {
      fadeOutTime = 400;
    }
    
    if (fadeInTime == null) {
      fadeInTime = 400;
    }
    
    (function(_this, content, fadeOutTime, fadeInTime) {
      _this.each(function(index, element) {
        Drupal.detachBehaviors($(element), Drupal.settings);
        $(element).fadeOut(fadeOutTime, function() {
          var replacementElement = $(content);
          replacementElement.hide();
          $(element).replaceWith(replacementElement);
          replacementElement.fadeIn(fadeInTime);
          
          Drupal.attachBehaviors(replacementElement.parent(), Drupal.settings);
        });
      });
    })(this, content, fadeOutTime, fadeInTime);
  };
})(jQuery);

$form['node_box'] = array(
        '#type' => 'markup',
        '#prefix' => '<div id="nodes_box">',
        '#suffix' => '</div>',
        '#markup' => $rendered_node
    );

function blocknify_submit_driven_callback($form, $form_state)
{

    $nid = $form_state['values']['dropdown_first'];
    $rendered_node = drupal_render(node_view(node_load($nid)));
    $commands[] = ajax_command_invoke('#nodes_box', 'fadeReplaceWith', array($rendered_node, 500, 400));

    return array(
        '#type' => 'ajax',
        '#commands' => $commands,
    );
}