drupal 8 render node programmatically

JavaScript
$nid = 1;
$entity_type = 'node';
$view_mode = 'teaser';

$view_builder = \Drupal::entityTypeManager()->getViewBuilder($entity_type);
$storage = \Drupal::entityTypeManager()->getStorage($entity_type);
$node = $storage->load($nid);
$build = $view_builder->view($node, $view_mode);
Source

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