in Helper/MagentoDataHelper.php [223:235]
public function getCartNumItems()
{
$cart = $this->objectManager->get(\Magento\Checkout\Model\Cart::class);
if (!$cart || !$cart->getQuote()) {
return null;
}
$numItems = 0;
$items = $cart->getQuote()->getAllVisibleItems();
foreach ($items as $item) {
$numItems += $item->getQty();
}
return $numItems;
}