Render a Node or an Entity

On drupal 8 every elements (almost) are an entity, as any entity you can render a node.

Display a node

$entity_type = 'node';

$entity_id = '1';

$view_mode = 'full';

$entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($entity_id);

$view_builder = \Drupal::entityTypeManager()->getViewBuilder($entity_type);

$pre_render = $view_builder->view($entity, $view_mode);

$build[] = $pre_render;

// OR to get HTML

//$html = render($pre_render);

//Note : you can also use if you don't want to use different entity types.

$node = Node::load($nid);

Display a view

$view = Views::getView('who_s_online');

if (is_object($view)) {

  $view->setDisplay('who_s_online_block');

  $view->preExecute();

  $view->execute();

  $output = $view->buildRenderable();

}

Render a node field

$view_builder = \Drupal::entityTypeManager()->getViewBuilder('node');

$storage = \Drupal::entityTypeManager()->getStorage('node');

$nid = 1;

$node = $storage->load($nid);

$view = $view_builder->viewField($node->get('body'), [

'type' => 'string', // string, entity_reference_label

'label' => 'hidden',

'settings' => ['link' => FALSE],

]);

$output = render($view);

Note : If you want to just get a value, you cal also do like this.

$value= Node::load($nid)->get('body')->value;