Adding image in the same Array React

Question

Hello I'm having a problem in uploading additional product image in my array. The URL is duplicated when I uploaded 2 files. The result will be like this.

{
    "url": "https://localhost:8000/1650517557416.jpg,https://localhost:8000/1650517559319.png",
}, {
    "url": "https://localhost:8000/1650517557416.jpg,https://localhost:8000/1650517559319.png",
}

Here is my frontend

export const addAdditionalProductPictures = async (images, productId, url) => {
    const ls = new SecureLS({ encodingType: "aes" });

    const token = ls.get("token");

    const formdata = new FormData();


    for (let index = 0; index < images.length; index++) {
        formdata.append("file", images[index]);
    }

    formdata.append("url", url);

    return await fetch(`${API}/product/image/${productId}`, {
        method: "POST",
        headers: {
            Authorization: `Bearer ${token}`,
        },
        body: formdata,
    })
        .then((response) => {
            return response;
        })
        .catch((err) => {
            //console.log(err)
            return err;
        });
};

Here is my backend

exports.addImage = (req, res) => {
const { url } = req.body

    let newImages = req.files.map(function (obj) {
      const id = mongoose.Types.ObjectId();
      return ({
        url: url,
      });
    });

    Product.findByIdAndUpdate(req.params.id, { $addToSet: { images: newImages }} , { new: true 
    }, (err, product)=> {
        if (err) {
            return res.status(400).json({
                error: dbErrorHandler(err)
            });
        }
        res.json(product);
    });

}

And here is my implementation on frontend

<Button
                            autoFocus
                            color="inherit"
                            type="submit"
                            disabled={isSubmitting}
                            onClick={async () => {
                                setIsSubmitting(true);

                                let filesUrls = [];
                                for (var i = 0; i < selectedImageFiles.length; i++) {
                                    const urlLink = await generateUploadUrl(
                                        selectedImageFiles[i].type
                                    );

                                    const to_base64 = (file) =>
                                        new Promise((resolve, reject) => {
                                            const reader = new FileReader();
                                            reader.readAsDataURL(file);
                                            reader.onload = () => resolve(reader.result);
                                            reader.onerror = (error) => reject(error);
                                        });

                                    let blob = await to_base64(selectedImageFiles[i]);
                                    let binary = atob(blob.split(",")[1]);

                                    let array = [];
                                    for (var x = 0; x < binary.length; x++) {
                                        array.push(binary.charCodeAt(x));
                                    }

                                    let blobData = new Blob([new Uint8Array(array)], {
                                        type: selectedImageFiles[i].type,
                                    });

                                    const uploadImageLink = await 
                                                          uploadImage(urlLink,blobData);
                                    const newUploadImageLink = uploadImageLink.url.split("?") 
                                      [0];
                                    filesUrls.push(newUploadImageLink);
                                }
                                addAdditionalProductPictures(
                                    selectedImageFiles,
                                    product?._id,
                                    filesUrls
                                )
                                    .then((response) => {
                                        if (response.status === 200) {
                                            response?.json().then((e) => {                                                   
                                             setIsSubmitting(false);
                                            });
                                        } else {
                                            response?.json().then((e) => {
                                                setIsSubmitting(false);
                                            });
                                        }
                                    })
                                    .catch((e) => console.log(e));
                            }}
                        >

I cannot get the URL from the AWS in the console in the backend. it returns me undefined. What is missing or what is wrong in my code?