drupal/core/modules/media/js/form.js

/**
* DO NOT EDIT THIS FILE.
* See the following change record for more information,
* https://www.drupal.org/node/2815083
* @preserve
**/

(function ($, Drupal) {
  Drupal.behaviors.mediaFormSummaries = {
    attach: function attach(context) {
      var $context = $(context);

      $context.find('.media-form-author').drupalSetSummary(function (context) {
        var $authorContext = $(context);
        var name = $authorContext.find('.field--name-uid input').val();
        var date = $authorContext.find('.field--name-created input').val();

        if (name && date) {
          return Drupal.t('By @name on @date', { '@name': name, '@date': date });
        } else if (name) {
          return Drupal.t('By @name', { '@name': name });
        } else if (date) {
          return Drupal.t('Authored on @date', { '@date': date });
        }
      });
    }
  };
})(jQuery, Drupal);