[予約]Shopifyでの商品ごとに異なる発送予定日を注文情報に出力する方法(開発者向け)

{% liquid
	assign latestEstimatedShipDate = 'today' | date: '%s'
	assign isPreorderInCart = false

	for item in cart.items
		if item.product.tags contains 'pre-order'
			assign isPreorderInCart = true
			assign curretItemDeliverDate = item.product.metafields.preorder.deliver-date | date: '%s'
			if latestEstimatedShipDate < curretItemDeliverDate and item.product.metafields.preorder.deliver-date != blank
				assign latestEstimatedShipDate = curretItemDeliverDate
			endif
		endif
	endfor
%}

{% if isPreorderInCart %}
	<p class="cart-attribute__field">
	  <label for="pre-order-deliver-date">Pre-order-deliver-date</label>
	  <input id="pre-order-deliver-date" type="text" name="attributes[Pre-order-deliver-date]" value="{{ latestEstimatedShipDate | date: '%Y-%m-%d' }}">
	</p>
{% endif %}

function getLatestShippingDate(cartPreOrderItems) {
	let latestEstimatedShippingDate = new Date().getTime();
	for (const item of cartPreOrderItems) {
		if (latestEstimatedShippingDate < new Date(item.shippingDate).getTime()) {
			latestEstimatedShippingDate = new Date(item.shippingDate).getTime();
		}
	}
	return new Date(latestEstimatedShippingDate);
}

function updateShippingDateAttribute(shippingDate) {
  
  const formData = JSON.stringify({
    attributes: {
      'Pre-order-deliver-date': shippingDate,
    }
  });

  fetch('cart/update.js', {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: formData
  })
  .then((response) => {
    if (!response.ok) {
      throw new Error('Network response was not ok');
    }
    return response.json();
  })
  .catch((error) => {
    console.error('Fetch error:', error);
  });
}

const cartPreOrderItems = document.querySelectorAll(".pre-order").getAttribute('deliveryDate');
updateShippingDateAttribute(getLatestShippingDate(cartPreOrderItems));