Implementing Deferred Purchase Options in the Shopify App

Shopify Apps
,
1

I want to ask about the docs about implement deferred purchase options (Pre-Order). It seems that the docs for that don’t provide enough information. This is the docs: https://shopify.dev/docs/apps/selling-strategies/purchase-options/deferred#building-deferred-purchase-options-in-your-app

I have followed all the steps, however I am still struggling with how to implement deferred purchase options (Pre-Order) in my app. I have used AJAX for adding item to the cart along with the selling_plan but somehow the AJAX cart API return blank object.

jQuery.post(‘/cart/add.js’, {
items: [{
quantity: 1,
id: 42958309949614,
selling_plan: 2633728174
}]
});

Also, I have “Only show this product with these purchase options” tick true on a product, but when I add that product to cart it still provide the blank object and can’t provide the selling plan attrubute in the response.