Drupal 8 notes

$current_url = \Drupal\Core\Url::fromRoute('<current>', array(), array("absolute" => TRUE))->toString();  // get full url

Drupal\Core\Site\Settings::get('some_setting_here'); // Get a setting from settings.php

$id = $node->id(); // get node id
$node_type = $node->getType(); // get node type

// get terms ids related to node
$terms = $node->get('field_sometaxonomyfield')->getValue();
$terms = array_column($terms, 'target_id');

{{ url('<current>') }}

Raw value of a field

{{ node.field_somefield.value }}

print image from image_field

{{ content.field_imagefield.0 }}