问如何使firebase函数(在create上使用)返回我可以从自己的react本机应用程序捕获的错误

EN

exports.countOrderProductChange = functions.firestore.document("/orders/{id}")
    .onCreate((change, context) => {
      const data = change.data();
      const itemsList = data["itemsList"];
      let error = "";

      const newProductsSizes = {};

      for (const item of itemsList) {
        db.collection("products").doc(item.product.id).get().then((doc) => {
          const product = doc.data();
          let sizes = [];
          if (item.product.id in newProductsSizes) {
            sizes = newProductsSizes[item.product.id];
          } else {
            sizes = product.sizes;
          }

          const remaingSize = sizes.find((size) => (size.name == item.size));
          const remaingSizeQty = remaingSize.qty;

          if (remaingSizeQty < item.qty) {
            if (remaingSizeQty == 0) {
              error = "Sorry there's no more (" + item.size +
               ") size of the product: " + item.product.name;
            } else {
              error = "Sorry there's only "+ remaingSizeQty +
              " of (" + item.size +
              ") size of the product: " + item.product.name;
            }
            functions.logger.log(error);
            return error;
          } else {
            const sizeIndex = sizes.findIndex((obj) => (obj.name == item.size));
            const newQty = remaingSizeQty - item.qty;
            const newSizes = sizes;
            newSizes[sizeIndex].qty = newQty;

            newProductsSizes[item.product.id] = newSizes;
          }
        });
      }
      for (const productId in Object.keys(newProductsSizes)) {
        if (Object.prototype.isPrototypeOf.call(newProductsSizes, productId)) {
          db.collection("products").doc(productId).update({
            sizes: newProductsSizes[productId],
          });
        }
      }
});