Show Inventory Levels By Location On Your Product Page

When someone visits your product page and the inventory check runs, this step receives the variant ID through a query parameter in the URL. The trigger is automatically configured to accept web requests and includes CORS headers to allow cross-origin requests from your storefront. It captures the variant_id from the query string and passes this essential identifier to the next step for inventory lookup. No manual configuration is needed - the trigger handles all incoming requests automatically.

The custom code takes the variant ID from the previous step and builds a GraphQL query to retrieve inventory levels across all locations. It specifically looks up the product variant, gets its inventory item, and returns the available quantities for each location name. The script uses MESA's built-in Shopify GraphQL connection, so authentication is handled automatically. The response includes location names paired with their available inventory counts, which gets returned as structured JSON data for your frontend to display.

const Mesa = require('vendor/Mesa.js');
const ShopifyGraphql = require('vendor/ShopifyGraphql.js');

/**
 * A Mesa Script exports a class with a script() method.
 */
module.exports = new class {
  script = (payload, context) => {
    let vars = context.steps;
    let variantId = vars.webrequest.querystring.variant_id;
    
    let query = `
      {
        productVariant(id:"gid://shopify/ProductVariant/${variantId}") {
          sku
          inventoryItem {
            inventoryLevels(first:10) {
              nodes {
                location {
                  name
                }
                quantities(names:"available") {
                  available: quantity
                }
              }
            }
          }
        }
      }
    `;

    const r = ShopifyGraphql.send(query, null);

    Mesa.output.next({"response": r.data.productVariant.inventoryItem.inventoryLevels.nodes});
  }
}