React - context not updating correctly

Question

I have the following component which is being used in a SweetAlert popup:

import React, {useContext, useState} from "react";
import {CartContext} from "../../../context/CartContext";

import styles from './ShoppingCartQuantity.module.css'

export const withShoppingCartContext = Component => props => {
    const { cart, removeItem, updateCart } = useContext(CartContext);
    return <Component {...props} {...{ cart, removeItem, updateCart }} />;
}

const ShoppingCartQuantity = ({ qty, productId, updateCart }) => {
    const [quantity, setQuantity] = useState(qty);

    const updateCartHandler = (productId, amount) => {
        setQuantity(Math.max(quantity + amount, 1));
        updateCart(productId, amount);
    }

    return (
        <div>
            <span>
                <span
                    className={`${styles.op} ${styles.decrementBtn}`}
                    onClick={() => updateCartHandler(productId, -1)}
                >
                  -
                </span>
                <span className={styles.qty}>{quantity}</span>
                <span
                    className={`${styles.op} ${styles.incrementBtn}`}
                    onClick={() => updateCartHandler(productId, 1)}
                >
                  +
                </span>
            </span>
        </div>
    )
}

export default ShoppingCartQuantity;

Here's a visual of the component:

I am using this component to update this context:

import React, {createContext, useEffect, useState} from "react";

export const CartContext = createContext();

const CartContextProvider = (props) => {
    const [cart, setCart] = useState(JSON.parse(localStorage.getItem('cart')) || []);

    useEffect(() => {
        localStorage.setItem('cart', JSON.stringify(cart));
        console.log(cart);
    }, [cart]);

    const updateCart = (productId, amount) => {
        if (cart.some(item => item.id === productId)) {
            setCart(cart => cart.map(item => item.id === productId
                ? {
                    ...item,
                    qty: Math.max(item.qty + amount, 1),
                }
                : item
            ));
        } else {
            const item = {
                id: productId,
                qty: 1              
            }

            const updatedCart = [...cart, item];
            setCart(updatedCart);
        }
        console.log(cart);
    }

    const removeItem = (id) => {
        setCart(cart.filter(item => item.id !== id));
    };

    return (
        <CartContext.Provider value={{cart, updateCart, removeItem}}>
            {props.children}
        </CartContext.Provider>
    )
};

export default CartContextProvider;

When I open the popup for the first time the initial value is 0 and when I click the increment button, no matter how many times I click it, the 2 console.log give me the following results:

So in the updateCart function, cart is always empty and in useEffect the cart has the required id but not the required qty as it should have been 4 since I clicked 4 times on the increment button.

Now If I close the popup and open it again, it displays the quantity 1(not 4) as this is the current state. If I start to increment(let's say 4 times) again, this is the result of the console.logs:

Now the useEffect gets the correct qty.

So, from what I understood, if an id is not in the cart array initially, no matter how much I increment it will always be added with qty 1 but if the id is already in the array, the increment works correctly.

What can I do to solve this issue?

Answer 1

the problem is coming from your updateCart Funtion