How to change values for previous content nodes drupal 8

Code snippet that can be used to change values for previous content nodes in drupal 8 when you add custom fields to your content type.

/**
 *  run cron
 */
function mymodule_cron(){
    $nids = \Drupal::entityQuery('node')
        ->condition('type', 'article', '=')
        ->execute();

    $nodes = \Drupal::entityTypeManager()->getStorage('node')->loadMultiple($nids);

    foreach ($nodes as $node) {
        $node->set('field_category', ['target_id' => 66]);
        $node->set('field_sub_category', ['target_id' => 69]);
        $node->set('field_image', ['target_id' => 1]);
        $node->save();
    }
}

Don't forget to comment this code after you run cron.