Shopify cart/update.js endpoint not updating the correct lineitem

Solution:

In that case (multiple lines with same variant id in the cart) is better to usechange.js instead ofupdate.js: https://shopify.dev/api/ajax/reference/cart#post-locale-cart-change-js (https://shopify.dev/api/ajax/reference/cart#post-locale-cart-change-js)

I'm doing like this:

$.ajax({
    type: "post", url: "/cart/change.js", data: [
        {"quantity": 2, "line": 0},
        {"quantity": 4, "line": 1},
    ], dataType: 'json'
});
Copy code

You see that I don't use thevariantId but I'm using the line index. The downside of this approach is that if you need to apply a change to all the same variant ids you need to know which lines have to be changed. But that can be done reading the respone fromcart.js

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