I am making a simple website.. i use react, MongoDB, JavaScript. My Problem is when click delivered button the quantity increase i update my UI and MongoDB Server. When Code is run in MongoDB server quantity is null..

Here is the code

const handleDelivered = data => {
        const { quantity, ...rest } = bookItem;
        const quantity1 = parseInt(bookItem.quantity) - 1;
        const quantityStr = quantity1.toString();
        const newQuantity = { quantity: quantityStr, ...rest }
        setBookItem(newQuantity);

        const getquantity = bookItem.quantity;
        console.log(getquantity);
        const updateQuantity = { getquantity };
        const url = `http://localhost:5000/items/${itemsId}`;
        fetch(url, {
            method: 'PUT',
            headers: {
                'content-type': 'application/json'
            },
            body: JSON.stringify(updateQuantity)
        })
            .then(res => res.json())
            .then(data => {
                console.log(data);
            })
    }