Code snippet that show you helpful node methods in Drupal 8.
// Get node type.
$node_type = $node->getType();
// Get node title.
$title = $node->getTitle();
// Get node status.
$visible = $node->isPublished();
// Get node promoted status.
$node->setPromoted(TRUE);
// Get node uid.
$uid = $node->getOwnerId();
// Get node user account.
$author = $node->getOwner();
