jquery - How to update line item properties in shopify

Solution:

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Theupdate endpoint can update multiple products at once, but cannot change the line-item properties.

You're looking for thechange endpoint, which can modify a single line in greater detail.

$.ajax({
        url: "/cart/change.js",
        type: "POST",
        data: '{"id":"1234567890", "quantity": 1, "properties":{ "Someprop": "Somevalue" } }', 
        contentType: "application/json",
        dataType: 'json'
    }
});
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NOTE: The data must contain either "line" (1-based index of item's position in the cart.items array) or "id" (which can either be the item'sid orkey value). I recommend updating using theitem.key for the ID field when using both the /change and the /update endpoints:id is just the variant ID, and when using line-item properties the same ID can therefore be repeated across multiple lines. Thekey is guaranteed to be unique.

Additionally, when hitting the /cart/change endpoint, if you do not specify the quantity parameter Shopify may default the line's quantity to 1. To be safe, I would recommend always explicitly passing the line's current quantity.

Note that Shopify will replace the line-item properties for the edited item with the line-item properties object that you supply. Per Corey's comment, the safest thing to do when updating a line item's properties is to get the existing properties for the line, update the value(s) that need updating, then hit the/cart/change.js endpoint with the updated object.

Additionally, per Bart Coppens' observation in the comments, an empty properties object is ignored by Shopify. This makes deleting all properties from a line item a bit problematic. The best workaround I have been able to come up with so far is to use a placeholder value whose key begins with an underscore, as the leading underscore causes Shopify to hide the property on the Checkout. (For example, I might use_validated: true/false). If your theme doesn't already hide properties with a leading underscore, find the properties loop (usually beginning withfor p in item.properties) and add the following:

{% if p.first.first == '_' %} {% continue %} {% endif %}
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