Adapting to Modern JS Syntax in Redux v5.0.0

Anton Ioffe - January 8th 2024 - 10 minutes read

As Redux v5.0.0 ushers in a new era of state management with its embracement of JavaScript's syntactical maturation, developers stand at the crossroads of innovation and compatibility. This article delves deep into the interplay between the ECMAScript Modules and CommonJS within Redux's latest offering, guiding the seasoned developer through the transformative process of adapting their codebases. We transcend beyond mere syntax enhancement, exploring modular compatibility's effects on performance and uncovering common integration pitfalls. Join us in envisaging the future of Redux modules, where your insights and adaptability shape the robust, scalable applications of tomorrow. Prepare to infuse your projects with the essence of modern JavaScript, ensuring that your Redux-driven development journey not only parallels the evolution of the language but thrives at its cutting edge.

Module System Renaissance: ESM Meets CJS in Redux v5.0

Redux v5.0.0 ushers in a paradigmatic shift with its integration of ECMAScript Modules (ESM) alongside the venerable CommonJS (CJS) module system. This fusion brings to the forefront a shared namespace where developers can tap into the strengths of both systems without sacrificing compatibility. By introducing a dynamic exports field in package.json, Redux ensures that when a developer writes an import statement such as import { createStore } from 'redux';, the bundler or runtime environment seamlessly selects the appropriate module format. The result is an acceleration in development velocity as developers no longer need to be mired in configuration details to ensure correct module resolution.

The use of both ESM and CJS within Redux poses a challenge in maintaining coherent exported members, as discrepancies can arise from non-matching export and require semantics. For instance, exporting Redux enhancers are commonly done through default exports in ESM, but when they are required in CJS modules, developers must adapt to different import styles. The correct approach in an ESM file would be export default myEnhancer;, while in a CJS setting, it is imported with const myEnhancer = require('myEnhancer').default;. This ensures that the enhancer is properly imported regardless of the module system in use, preventing runtime errors and maintaining functional consistency.

To underscore the cross-compatibility intentions of Redux v5.0.0, consider how actions—a common aspect of Redux applications—are handled. Ideally, actions should be framework-agnostic, hence written in a way that ensures seamless sharing between both ESM and CJS modules. For instance:

// action.js - Using ESM syntax
export const myAction = { type: 'MY_ACTION_TYPE' };

// In a CJS module
const { myAction } = require('./action');

This example illustrates that by exporting individual members and destructuring upon require, developers can bridge the gap between the two systems without causing namespace or interoperability conflicts.

Addressing middleware, such as Redux thunk, presents a unique scenario in hybrid environments. A Redux thunk middleware must be crafted to cater to both module types, which warrants explicit attention to how exports are structured. The middleware would be written and exported like so in an ESM file:

// reduxThunkMiddleware.mjs
export default function reduxThunkMiddleware({ dispatch, getState }) {
    return next => action => {
        // Thunk logic goes here

Then, in a CJS environment, it can be included via const reduxThunkMiddleware = require('./reduxThunkMiddleware.mjs').default;. This illustrates the requisite mindfulness when dealing with function exports to achieve fluid functionality in both ESM and CJS contexts.

Lastly, with Redux's shift towards ESM as the primary module artifact comes a direct impact on build systems and module interoperability. Tools like webpack now favor ESM for its static analysis and treeshaking capabilities, which can significantly reduce final bundle sizes. While developers may enjoy the performance benefits, they must also be cognizant of the implications: ESM should be indicated as the main module format whenever possible, while still providing CJS fallbacks to support the existing ecosystem. Such a consciousness in configuration is paramount to harness the full potential of Redux v5.0.0 without sacrificing the broad compatibility required for today's diverse JavaScript landscape.

Under the Hood: Refactoring Redux Codebases for Modular Compatibility

When undertaking the refurbishment of a Redux codebase to comply with the enhanced structure introduced in Redux Toolkit, it is paramount to pivot smoothly to configureStore. This method not only simplifies store setup by applying essential middleware and enhancers out-of-the-box but also encourages the adoption of resilient patterns aligned with best practices. As part of this shift, developers should adjust their focus to seamless integration with TypeScript, thus weaving type-safety into the very fabric of their state management logic.

import { configureStore } from '@reduxjs/toolkit';
import rootReducer from './slices';

export const store = configureStore({
  reducer: rootReducer,
  // Additional store setup and configuration can go here

Furthermore, refactoring the API call state management to a modular approach allows individually crafted slices of state to encompass the entire lifecycle of an API call. This avoids a monolithic structure and facilitates scalability. It becomes increasingly beneficial to leverage Redux Toolkit slices to encapsulate and manage separate concerns of the application state. Such slices are concretely typed with TypeScript, thus ensuring that dispatches and selectors interoperate with reliable type checks.

import { createSlice, createAsyncThunk, PayloadAction } from '@reduxjs/toolkit';

export const fetchData = createAsyncThunk('data/fetch', async (params, { getState }) => {
  // Perform asynchronous operations here

const dataSlice = createSlice({
  name: 'data',
  initialState: { entities: [], loading: 'idle' },
  reducers: {
    // Standard reducer logic
  extraReducers: (builder) => {
    builder.addCase(fetchData.pending, (state, action) => {
      state.loading = 'pending';
    .addCase(fetchData.fulfilled, (state, action) => {
      state.entities = action.payload;
      state.loading = 'idle';
    .addCase(fetchData.rejected, (state, action) => {
      state.loading = 'failed';

export const { actions, reducer } = dataSlice;

To enhance the performance, store modularization plays a central role. Dividing the store into multiple slices, as demonstrated above, leads to more maintainable and optimized code. Such modularization directly benefits performance by making state updates and retrievals more efficient. Smaller, focused slices mean that components re-render only when their specific part of the state changes, preventing unnecessary updates and conserving valuable computational resources.

During refactoring, it is also crucial to ensure that existing middleware integrates seamlessly with the new configureStore setup. Custom middleware or integration with third-party libraries should be re-evaluated to confirm compatibility and maximize the potential of Redux Toolkit optimizations. This can often involve wrapping middleware to conform to the new Redux ecosystem, potentially reducing boilerplate while preserving high-performing asynchronous data flow patterns.

import { configureStore, getDefaultMiddleware } from '@reduxjs/toolkit';
import customMiddleware from './customMiddleware';

export const store = configureStore({
  reducer: rootReducer,
  middleware: (getDefaultMiddleware) => getDefaultMiddleware().concat(customMiddleware),

In summary, state management via Redux has been brought to a new echelon with the advent of TypeScript and Redux Toolkit. The refactoring process should be embraced as an opportunity to bolster type safety, reinforce modular structures, and refine performance. This strategic reconstruction primes Redux codebases for the evolving challenges of modern web development, paving the way for systems that are not only easier to maintain but are also ready for future technological advancements.

Tuning Performance in the ESM-CJS Hybrid Terrain

To harness the full potential of tree shaking within Redux v5.0.0, it is imperative to instruct the bundler on which files can safely have their unused exports removed. This is done via the "sideEffects": false declaration in package.json, signaling that the files are free of side effects and hence eligible for tree shaking. It can have a significant impact on the bundle size, especially when paired with ESM's static structure:

// package.json
  "sideEffects": false

Utilizing lazy loading strategies with ESM's import() function enhances the performance of Redux stores by minimizing the initial payload and delaying the loading of non-essential code. The conceptual shift to loading middleware asynchronously provides a glimpse into the more efficient, modular approach facilitated by ESM:

import { createStore, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import rootReducer from './rootReducer';

let store = createStore(

// Async middleware application function
async function loadAndApplyMiddleware(middlewareModulePath) {
  const { default: newMiddleware } = await import(middlewareModulePath);
  const middlewareAPI = {
    getState: store.getState,
    dispatch: (...args) => store.dispatch(...args)
  const getMiddleware = () => [thunk, newMiddleware()].map(middleware => middleware(middlewareAPI));
  store = createStore(

In bridging ESM and CJS within Redux setup, attention to the form of import statements is paramount. The correct usage ensures seamless interoperability. Here is the correct approach to importing a CJS module within an ESM-dominant environment:

// Redux store setup with ESM syntax importing CJS reducer
import cjsReducer from './cjsReducer.cjs';
import { createStore } from 'redux';

export const store = createStore(
  // applyMiddleware and other store enhancers

When it comes to exports, choosing between named and default exports can influence the effectiveness of tree shaking, with named exports being more transparent. Bundlers can optimize for either when free of side effects, enhancing modularity and clarity:

// actionCreators.js using ESM syntax
export function addUser(user) {
  return { type: 'ADD_USER', user };
export function removeUser(userId) {
  return { type: 'REMOVE_USER', userId };

A wise approach to Redux store management involves component-level code splitting using React's dynamic React.lazy and Suspense mechanisms, promoting even more granular control over the loading process:

import React, { useEffect, Suspense, lazy } from 'react';

const LazyUserComponent = lazy(() => import('./UserComponent'));

const App = () => (
  <Suspense fallback={<div>Loading...</div>}>
    <LazyUserComponent />

Sidestepping the Pitfalls: Common Redux Module Compatibility Errors

Avoiding mix-ups between named and default exports is crucial when working with Redux v5.0.0. A frequent misstep occurs when a developer exports a reducer as default using ESM syntax but then tries to import it using named import syntax within a CJS module. To import the reducer correctly in a CJS module, the require statement should not use destructuring, like so:

// Incorrect import in CJS
const { reducer } = require('./reducer');

// Correct import in CJS
const reducer = require('./reducer').default;

Such mismatches can cause silent failures, as the incorrectly imported entity will be undefined, possibly leading to errors only surfacing at runtime.

Compatibility between ESM and CJS does not only concern static imports. The dynamic import of stores must also be handled with care. Developers may attempt to use require() dynamically, which is not a direct counterpart to ESM's import():

// Incorrect dynamic import using require in CJS
let store;
if (condition) {
  store = require('./');
} else {
  store = require('./');

// Correct dynamic import using import() in ESM
let storePromise;
if (condition) {
  storePromise = import('./');
} else {
  storePromise = import('./');
storePromise.then(module => {
  const store = module.default;
  // Use store...

Bundler misconfigurations are another common pitfall. Some build systems might not differentiate between module formats or improperly handle the "exports" field in package.json, which can lead to module resolution errors. Ensuring that bundlers are appropriately configured and updated to support the "exports" field is imperative. Without this attention to detail, developers could end up with build-time errors or unpredictable behavior in their applications.

Misuse of default imports can arise when attempting to share Redux actions between ESM and CJS modules. A common mistake is to re-export a named export as default in an ESM module, causing inconsistencies. To share Redux actions while maintaining compatibility, one must be consistent in the export style:

// action.js (ESM)
export const someAction = { type: 'SOME_ACTION' };

// Incorrect re-export as default in another ESM module
export { someAction as default };

// Correct sharing of named export in a CJS module
const { someAction } = require('./action');

Developers may also run into issues with improperly exported Redux thunk middleware, leading to non-operable middleware in one module format or the other. It is essential that the middleware is exported to support both module types:

// Incorrect export of Redux thunk middleware in ESM
export default myMiddleware;

// Correct exports for Redux thunk middleware in ESM
export const myMiddleware = store => next => action => {
  // Middleware logic here...

// Correct usage in a CJS module
const { myMiddleware } = require('./myMiddleware');

By anticipating these common conflicts and applying the correct code patterns, developers can promote a smoother transition to the blended module ecosystem provided by Redux v5.0.0, aiding in seamless module integration across their applications.

Envisioning the Future of Redux Modules

As JavaScript continues to evolve, Redux's modular approach is poised to become even more nuanced and strategic. Envision the middleware of tomorrow, as dynamic loading allows each slice of state to be paired with the precise middleware it requires. This vision foretells a future where middleware is not just a static inclusion but a dynamic, context-aware actor in the application lifecycle. One can imagine middleware that is as responsive as the application state itself, enhancing performance by only consuming resources when necessary and improving memory usage significantly for complex applications.

The potential for API modularization is clear. The very heart of Redux could shift from a holistic framework to a finely-tuned array of modular utilities, ready to be handpicked and assembled like components into a powerful, yet lean machine. The advantages here are manifest; a lighter load not just in kilobytes but in cognitive overhead. What new best practices will emerge from developers being able to choose only what is necessary for their projects? Could this lead to a situation where the grunt work of boilerplate setup gives way to a tailored, minimalist approach?

It is the insights and contributions from developers that will shape Redux's trajectory. Their feedback will be the kiln wherein new ideas are fired into the sturdy bricks of Redux's future. How will developers' real-world experiences influence the balance Redux strikes between flexibility and a streamlined API? As Redux developers adapt to and adopt these changes, are we likely to see a divergence in the familiar patterns of state management, and what innovations will spring forth from this metamorphosis?

Developers stand on the precipice of a new horizon, surveying a landscape where Redux modules are integral to crafting state management systems of the future. How will the dual-module paradigm transform Redux's integration with the wider JavaScript ecosystem? As we adopt modern JavaScript syntax and structures, Redux modules are not just being adapted to fit the current landscape—they have the potential to actively shape it. What are the opportunities for Redux to set new paradigms for how modularity and developer experience define the horizon of web development?

In this light, the future of Redux modules beckons questions of adaptability and resilience. Will the focus on modular design usher in an era of Redux that is embraced more as a suite of precise tools, rather than a single, encompassing solution? Developers need to stay astute, recognizing that adapting to modular advancements is not just about tackling the learning curve, it's about ensuring the evolution of their craft. As we accept and implement Redux's updated syntax, we not only keep pace with development trends but also take active roles in sculpting a sustainable and efficient future for web applications.


In this article, the author explores the impact of the integration of ECMAScript Modules (ESM) and CommonJS (CJS) in Redux v5.0.0. They discuss the importance of adapting codebases to ensure compatibility between the two module systems and highlight potential pitfalls and challenges. The article emphasizes the benefits of using Redux Toolkit and TypeScript in refactoring Redux codebases to enhance performance and embrace modern web development practices. The key takeaway is that developers must stay adaptable and proactive in their use of modern JavaScript syntax and module systems to shape the future of Redux. The challenging technical task for readers is to refactor their Redux codebases to leverage the modular compatibility introduced in Redux v5.0.0, while also considering performance optimization techniques such as tree shaking and lazy loading.

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