const handleAddToUpdate = (selecteInventory) => {
    let newCart = [];
    const exists = inventorys.find(inventory => inventory.quantity === selecteInventory.quantity);
    if (!exists) {
        selecteInventory.quantity = parseInt();
        newCart = [...inventorys, selecteInventory];
    }
    else {
        const rest = inventorys.filter(inventory => inventory.quantity !== selecteInventory.quantity);
        exists.quantity = exists.quantity + 1;
        newCart = [...rest, exists];
    }
    setInventorys(newCart);
    // addToDb(selecteInventory.id);
}

<button className='btn btn-primary' onClick={() => handleAddToUpdate(inventory.quantity)}>UPDATE</button>`