Get the list of fields for an entity type

To get the field definitions of any entity type use the following code. We first get all bundles, and then for each bundle we are getting the field definitions.

$bundles = \Drupal::service('entity_type.bundle.info')->getBundleInfo('node');

foreach ($bundles as $bundle => $data) {
  $fields = \Drupal::service('entity_field.manager')->getFieldDefinitions('node', $bundle);
}