Drupal - How to create a multilingual node programmatically?

Fortunately I found a post named Create and translate a multilingual nodes programmatically.

And here is the code with some comments:

use Drupal\node\Entity\Node;

$node = Node::create([
  // The node entity bundle in this case article.
  'type' => 'article',
  //The base language
  'langcode' => 'en',
  'created' => \Drupal::time()->getRequestTime(),
  'changed' => \Drupal::time()->getRequestTime(),
  // The user ID.
  'uid' => 1,
  'title' => 'My test!',
  //If you have another field lets says field_day you can do this:
  //'field_day' => 'value',
  'body' => [
    'summary' => '',
    'value' => '<p>The body of my node.</p>',
    'format' => 'full_html',
  ],
]);
//Saving the node
$node->save();
//This line is not necessary
\Drupal::service('path.alias_storage')->save("/node/" . $node->id(), "/my/path", "en");

//Creating the translation Spanish in this case
$node_es = $node->addTranslation('es');
$node_es->title = 'Mi prueba!';
$node_es->body->value = '<p>El cuerpo de mi nodo.</p>';
$node_es->body->format = 'full_html';
//Saving the node
$node_es->save();
//This line is not necessary
\Drupal::service('path.alias_storage')->save("/node/" . $node->id(), "/mi/ruta", "es");

I was racking my brain over this problem in Drupal 8. Here's how I finally got it done, This code copies title, body, all fields, and the pathauto setting. I'm sure there's room for improvement here as some meta fields probably need to get processed too. But this should get you started!

// This assumes you have a $node variable that contains the node translation you're starting with
$node_trans = $node->addTranslation('en-au'); // sample using Australian English
$node_trans->setTitle($node->getTitle());
$node_trans_fields = $node->getTranslatableFields();
foreach ($node_trans_fields as $name => $field) {
  if (substr($name, 0, 6) == 'field_' || in_array($name, ['body', 'path', 'title'])) {
    $node_trans->set($name, $field->getValue());
  }
}
try {
  $node->save();
}
catch (\Exception $error) {
  $add_status .= 'ERROR saving ';
}