How do I update a record using the put API?

Question

As you can see in the React Js code I am trying the Reduce one by one quantity when clicking the Delivered button. When the Click Delivered button quantity becomes null.

   const reduceQuantity=(productId)=>{
        
            const quantityReduce=parseInt(product.quantity )- 1
            const url = `http://localhost:5000/product/${productId}`
            fetch(url, {
                method: "PUT",
                headers: {
                    "Content-Type": "application/json",
                },
                body: JSON.stringify({ quantityReduce }),
            })
                .then((res) => res.json())
                .then((data) => {
                    console.log('success', data)
                    
                });

return (
        <div className='item-container'>
            <div className='text-center'>
                <img src={product.picture} alt="" />
            </div>
            <h6><b>{product.name}</b></h6>
            <p className='text-justify'><b>Description:</b>{product.Description}</p>
            <div className='d-flex'>
                <div>
                    <p><b>Price:</b>{product.price}</p>
                    <p><b>supplierName:</b>{product.supplierName}</p>

                </div>
                <p><b>Quantity:</b>{product.quantity}</p>
            </div>
            
        </div>`enter code here`
        <div className='text-center d-flex justify-content-around'>
        <button className='btn btn-outline-success rounded-pill' >Delivered</button>
server Side API:
// update quantity of products
 

 app.put("/product/:id", async (req, res) => {
    const id = req.params.id;
    const data = req.body;
    console.log("from update api", data);
    const filter = { _id: ObjectId(id) };
    const options = { upsert: true };

    const updateDoc = {
      $set: {
        quantity: data.addQuantity 
      },
    };