Simple snippet on how to update node fields programmatically in drupal 8.
Fisrt import Node entity:
use Drupal\node\Entity\Node;
Then use below code inside a function where you want to update the nodes.
/**
* hook_cron(): called every time the Drupal cron runs
*/
function mymodule_cron()
{
$query = \Drupal::entityQuery('node')
->condition('nid', '1');
$nids = $query->execute();
$nodes = Node::loadMultiple($nids);
foreach ($nodes as $node) {
$node->set("title", strtoupper($node->title->value));
$node->save();
}
\Drupal::messenger()->addMessage('Nodes updated');
}
