Apply discount to line item in cart: [NEED ATTENTION]

[thesunilyadav]

Hello Shopify community,

I'm currently working on developing an app that offers upsell functionality, allowing users to add items to their cart with discounts and free shipping. However, I'm facing an issue with applying the correct discount to the added items.

I've tried various methods using the AJAX API to add items to the cart, but unfortunately, the discounts are not being applied as intended. What I want is to add an item to the cart and have only that specific item receive the discount that was applied during the addition process.

I've spent considerable time researching and trying different approaches, but none have yielded the desired results. I've looked through multiple resources and attempted several possible workarounds, but they haven't worked as expected.

If anyone has experience with a similar issue or has insights into the proper way to apply discounts through the AJAX API when adding items to the cart, I would greatly appreciate your assistance

Try:1

This way it add item to cart but it removes the previous items from cart.

    let productId = 41172450050199;
    let quantity = 1;
    let discountCode = 'MY_CODE_23';
    let productUrl = `/cart/${productId}:${quantity}?discount=${discountCode}`;

    $.ajax({
    type: 'POST',
    url: productUrl,
    dataType: 'json',
    async: false,
    success: function (res) {
        console.log("Item added to cart. ", res);
    },
    error: function (res) {
        console.log("Error while adding item to cart. ", res);
    }
    });

Here MY_CODE_23 is created in Discount

Try:2

This way it adds item to cart but also adds the same discount for all available items in cart considering even if some item should not have discount.

      $.ajax({
        type: 'POST',
        url: '/cart/add.js',
        dataType: 'json',
        async: false,
        data: {
          items: [
            {
              id: 41172449558999,
              quantity: 1,
              properties: {},
            }
          ],
        },
        success: function (res) {
          console.log("item added to cart. ", res);
          applyDiscountCode(res.variant_id, 'MY_CODE_23');
        },
        error: function (res) {
          console.log("Error while adding item to cart. ", res);
        }
      });
      
      function applyDiscountCode(variantId, discountCode) {
        $.ajax({
          type: 'POST',
          url: '/cart/add.js',
          dataType: 'json',
          async: false,
          data: {
            id: variantId,
            quantity: 1,
            properties: {},
            discount_code: discountCode,
          },
          success: function (res) {
            console.log("Discount code applied. ", res);
          },
          error: function (res) {
            console.log("Error while applying discount code. ", res);
          }
        });
      } 

Here it add item into cart with discount but it throws error like: Required parameter missing or invalid: items

I've explored various other methods, but unfortunately, none of them have provided a valid solution. As time is of the essence, I need to complete this task as soon as possible. If anyone has any insights or suggestions that could be helpful in resolving this issue, I would be immensely grateful for your help.

Thank you for taking the time to read my post and for sharing your expertise!

[Liam]

Hi Thesunilyadav,

As you've seen the AJAX API does not support applying discounts to specific items in the cart. The discount code applies to the entire cart, not individual line items. Here's a few other options you could explore:

1. Product Discount Functions: This API allows you to set up discounts that apply to just specific products. There's a tutorial on our docs that shows how to set this up. However, only users on a Shopify Plus plan can create custom apps that contain Shopify Function APIs, but public apps on the Shopify app store can also use this functionality. 

2. Draft Orders allow you to apply discounts to specific line items. However, this would require a different checkout flow, as customers would need to be redirected to the draft order's checkout URL.

3. Price Rules: You could create a price rule that applies a discount to specific products. However, this would apply the discount to those products for all customers, not just those who added the item via your upsell functionality. You can see examples of how to implement price rules in our docs here.

Hope this helps!