React usereducer shopping cart duplicate items

Medium

You're implementing a shopping cart using React's useReducer. Which implementation correctly handles adding items while preventing duplicates and updating quantities?

ReactUsereducerReact hooksState managementArraysRedux+1

1const cartReducer = (state, action) => {
switch (action.type) {
  case 'ADD_ITEM': {
    const { id, name, price, quantity = 1 } = action.payload;
    
    // Complete this section
    const existingItem = state.find(item => item.id === id);
    if (existingItem) {
      return state.map(item =>
        item.id === id
          ? { ...item, quantity: /* MISSING CODE */ }
          : item
      );
    }
    
    return [...state, { id, name, price, quantity }];
  }
  default:
    return state;
}
21};

You're implementing a shopping cart using React's useReducer. Which implementation correctly handles adding items while preventing duplicates and updating quantities?

Hint