Building Forward-Compatible Slices with Redux Toolkit

Illustrate the best practices for designing and implementing custom slice reducers that anticipate future changes in JavaScript and Redux patterns.
import { createSlice, current } from '@reduxjs/toolkit';

// Define an initial state that can be easily extended or modified in future
const initialState = {
  items: [],
  totalAmount: 0

// Utilize createSlice to handle state logic in a predictable and modular way
const cartSlice = createSlice({
  name: 'cart',
  reducers: {
    // Best practice: Use action creators that can handle new properties without breaking changes
    addToCart(state, action) {
      const newItem = action.payload;
      // Future-proofing: Use immer's 'current' to snapshot state if needed for debug or undo features
      console.log('Current state', current(state));
      state.totalAmount += newItem.price * newItem.quantity;
    // Supporting function for future removal logic
    removeFromCart(state, action) {
      const id = action.payload;
      const existingItem = state.items.find(item => === id);
      if (existingItem) {
        state.totalAmount -= existingItem.price * existingItem.quantity;
        state.items = state.items.filter(item => !== id);
    // Add more reducers here following the same pattern

export const { addToCart, removeFromCart } = cartSlice.actions;
export default cartSlice.reducer;
This JavaScript code demonstrates the creation of a Redux cart slice with redux toolkit. The initial state is set up in a manner that allows for easy modifications for future requirements. Action creators like addToCart and removeFromCart are written to be flexible and maintainable.