++将值增加2而不是1

Question

export default (state, action) => {
    switch (action.type) {
        case 'ADD_PRODUCT':
            return {
                ...state,
                products: [action.payload, ...state.products]
            }
        case 'DELETE_PRODUCT':
            return {
                ...state,
                products: state.products.filter(product => product.id !== action.payload)
            }
        case 'ADD_TO_CART': if (state.cart.some(cartItem => cartItem.id === action.payload.id)) {
            const updatedItemIndex = state.cart.findIndex(cartItem => cartItem.id === action.payload.id)
            let cartItems = [...state.cart]
            let itemToUpdate = cartItems[updatedItemIndex]
            itemToUpdate.quantity++
            return { ...state, cart: cartItems }

        } else {
            const newItem = { ...action.payload, quantity: 1 }
            return { ...state, cart: [...state.cart, newItem] }
        }
        default:
            return state
    }
}

function addToCart(product) {
    dispatch({
        type: 'ADD_TO_CART',
        payload: product
    })
}

导出const ProductCard=（{product}）=>{const{deleteProduct,addToCart}=useContext（ProductContext）

const handleDelete = () => {
    deleteProduct(product.id)
}

const handleCart = () => {
    addToCart(product)
}


return (
    <div className='product__card'>
        <h3>{product.productName}</h3>
        <p>{product.price}</p>
        <button className='button'>View Product</button>
        <button onClick={handleCart} className='button'>Add to Cart</button>
        <button onClick={handleDelete} className='button'>Delete</button>
    </div>
)

}

Answer 1

我遇到过同样的问题，情况非常相似，目前的答案都没有帮助我。所以我只能推荐

itemToUpdate.quantity++

被改成

itemToUpdate.quantity += 0.5;

我知道这不是解决这个问题的正确方法，但功能是有效的，您可以在以后找到解决方案时更改它