How to update state in Context using Hooks in MERN Stack Application - node.js

Question

I'm trying to find a way to update my "user" state, but I'm stuck here for 3 days already, I need some help.
Here is my user context:
import React, {useEffect, useState} from 'react';
export const UserContext = React.createContext({})
const UserProvider = UserContext.Provider;
const UserContextProvider = (props) => {
const [user, setUser] = useState({})
useEffect(() => {
fetch(`${API}/auth/user`, {
method: 'GET',
withCredentials: true,
credentials: 'include'
})
.then (response => response.json())
.then (response => {
setUser(response.user)
})
.catch (error => {
console.error (error);
});
}, [setUser])
console.log(user)
return (
<UserProvider value={{user, setUser}}>
{props.children}
</UserProvider>
)
}
export default UserContextProvider;
Here is where I'm trying to update the user. In my case I'm trying to push an object in user.cart array, cuz everything on the back-end is fine, but in the front-end the state is not updating:
First I'm using the UserContext:
const Products = () => {
const {user, setUser} = useContext(UserContext) ...
And then here I'm trying to update the user state, BUT when I click the button it logged me out:
<button className="addTo--Cart--Button--Container">
<FaShoppingCart onClick={() => {addToCart(user._id, product); setUser(oldState => oldState.cart.push(product))}}/>
</button>
After this logged me out, the console.log(user) which is in UserContextProvider function log only the user.cart updated lenght.
AND one more:
How to remove item from context:
Here is my remove function:
const removeFromContextCart = (id) => {
console.log(id)
const updatedCart = user.cart.filter((item) => item.id !== id);
setUser(oldState => ({
...oldState,
cart: [
...oldState.cart,
updatedCart
]
}))
}
And my button:
<button className="remove--Button" onClick={() => {removeFromCart(user._id, product); setUser(removeFromContextCart(product._id))}}> REMOVE</button>

Answer 1

Try updating the user state in this way
setUser(oldState => ({
...oldState,
cart: [
...oldState.cart,
product
]
}))