Drupal Working with node fields programmatically

plugin.php

<?php

// Load node by nid:
$nid = 234; 
$node_storage = \Drupal::entityTypeManager()->getStorage('node');
$node = $node_storage->load($nid);

// Get node id:
$nid = $node->id();

// Get node/entity bundle:
$bundle = $node->bundle();   
$bundle = $entity->getType(); 

// Get field values:
$node->get('title')->value;           
$node->get('created')->value;      
$node->get('body')->value;          
$node->get('body')->summary;         
$node->get('field_foo')->value;     
$node->get('field_image')->target_id;

// You can also use a short entry to get the values:
$node->title->value;
$node->created->value;
$node->body->value;
$node->body->summary;
$node->field_foo->value;
$node->field_image->target_id;

// Loading specific nodes by field value:
$query = \Drupal::entityQuery('node')
  ->condition('type', 'article'),
  ->condition('field_terms', 42);
$nids = $query->execute();
$nodes = $node_storage->loadMultiple($nids);
  
foreach ($nodes as $node) {
  print $node->title->value;
  $node->set('title', "New title for node");
  $node->save();
}

// Change the values in the fields:
$node->set('title', "New title");
$node->set('body', array(
'summary' => "Teaser",
'value' => "Long text",
'format' => 'basic_html',
));
$node->save();

// Also for fields with a single value, you can use a short entry:
$node->title = 'New title';
$node->field_text = 'text';

// Getting the values of multiple fields:
$nids = \Drupal::entityQuery('node')->condition('type', 'album')->execute();
$nodes = Node::loadMultiple($nids);
 
$data = array();
foreach($nodes as $node) {
  $photo = array();
  foreach($node->get('field_image')->getValue() as $file){
    $fid = $file['target_id']; // get file fid;
    $photo[] = \Drupal\file\Entity\File::load($fid)->getFileUri();
  }
 
  $data[] = array(
    'album_name' => $node->get('field_album_name')->getValue(),
    'place' => $node->get('field_place')->getValue(),
    'author' => $node->get('field_author')->getValue(),
    'photo' => $photo,
  );
}