How to Implement Redux in 24 Lines of JavaScript

Redux has revolutionized the way we manage state in JavaScript applications. It provides a predictable and centralized approach to state management, making it easier to develop and maintain complex applications. In this article, we‘ll dive into the core concepts of Redux and learn how to implement it from scratch in just 24 lines of JavaScript. Let‘s get started!

Understanding Redux Principles

Before we jump into the implementation, let‘s familiarize ourselves with the three core principles of Redux:

1. Single source of truth: The entire state of your application is stored in a single JavaScript object called the "store". This makes it easy to track and manage the state changes throughout your app.

2. State is read-only: The only way to modify the state is by dispatching an action, which is a plain JavaScript object describing the change. This ensures that the state remains predictable and allows for easier debugging.

3. Changes are made with pure functions: To specify how the state tree is transformed by actions, you write pure reducers. Reducers are functions that take the previous state and an action, and return the next state without mutating the previous state.

Redux Architecture and Data Flow

Now that we understand the principles, let‘s explore the Redux architecture and how data flows through it.

1. Actions: Actions are plain JavaScript objects that describe what happened in your application. They typically have a type property indicating the type of action being performed, and may also include additional data.

const INCREMENT = ‘INCREMENT‘;
const DECREMENT = ‘DECREMENT‘;

const incrementAction = {
  type: INCREMENT
};

const decrementAction = {
  type: DECREMENT
};

2. Reducers: Reducers are pure functions that specify how the state changes in response to actions. They take the current state and an action, and return the next state. Reducers should always return a new state object instead of modifying the previous state.

const initialState = { count: 0 };

function counterReducer(state = initialState, action) {
  switch (action.type) {
    case INCREMENT:
      return { count: state.count + 1 };
    case DECREMENT:
      return { count: state.count - 1 };
    default:
      return state;
  }
}

3. Store: The store is the object that holds the application state and provides methods to access and update the state. It is created by passing the root reducer to the createStore function.

Implementing Redux in 24 Lines of JavaScript

Now that we have a solid understanding of the Redux architecture, let‘s implement it in JavaScript. We‘ll create a simple createStore function that encapsulates the Redux functionality.

function createStore(reducer, initialState) {
  let state = initialState;
  let listeners = [];

  function getState() {
    return state;
  }

  function dispatch(action) {
    state = reducer(state, action);
    listeners.forEach(listener => listener());
  }

  function subscribe(listener) {
    listeners.push(listener);
    return function unsubscribe() {
      const index = listeners.indexOf(listener);
      listeners.splice(index, 1);
    };
  }

  dispatch({ type: ‘@@INIT‘ });

  return {
    getState,
    dispatch,
    subscribe
  };
}

Let‘s break down the createStore function:

• It takes a reducer function and an optional initialState as arguments.
• The state variable holds the current state of the store.
• The listeners array stores the callback functions that will be invoked whenever the state changes.
• The getState function returns the current state.
• The dispatch function takes an action, passes it through the reducer along with the current state, and updates the state with the returned value. It then notifies all the subscribed listeners.
• The subscribe function allows components to subscribe to state changes. It takes a listener callback and returns an unsubscribe function to remove the listener.
• Finally, the createStore function returns an object with the getState, dispatch, and subscribe methods, providing access to the store‘s functionality.

Using Redux in a Counter Application

Let‘s see Redux in action by building a simple counter application. We‘ll create a store using our createStore function and connect it to the UI.

const store = createStore(counterReducer, { count: 0 });

const counterDisplay = document.getElementById(‘counter‘);
const incrementButton = document.getElementById(‘increment‘);
const decrementButton = document.getElementById(‘decrement‘);

function render() {
  counterDisplay.innerText = store.getState().count;
}

store.subscribe(render);
render();

incrementButton.addEventListener(‘click‘, () => {
  store.dispatch({ type: INCREMENT });
});

decrementButton.addEventListener(‘click‘, () => {
  store.dispatch({ type: DECREMENT });
});

In this example:

• We create a store using our createStore function, passing in the counterReducer and an initial state of { count: 0 }.
• We select the necessary DOM elements for displaying the counter value and handling button clicks.
• The render function is responsible for updating the UI with the current state value.
• We subscribe the render function to the store, so it gets called whenever the state changes.
• Finally, we attach click event listeners to the increment and decrement buttons, dispatching the corresponding actions when clicked.

Benefits and Use Cases of Redux

Redux offers several benefits that make it a popular choice for managing state in JavaScript applications:

1. Predictable state management: By following the Redux pattern, you can ensure that the state of your application remains predictable and easy to reason about. The single source of truth and the use of pure reducers make it easier to track and manage state changes.

2. Easier debugging and testing: With Redux, it becomes simpler to debug and test your application. You can easily track state changes, replay actions, and test reducers in isolation. Redux DevTools also provide powerful debugging capabilities, allowing you to inspect the state and travel back in time to specific actions.

3. Scalability and maintainability: As your application grows in complexity, Redux helps keep your code organized and maintainable. By separating concerns and enforcing a unidirectional data flow, Redux promotes a clean and scalable architecture. It also enables better code reuse and composition through the use of higher-order reducers and middleware.

Best Practices and Tips

When using Redux, there are some best practices and tips to keep in mind:

1. Keep the state minimal and normalized: Only store the minimal amount of data necessary in the Redux store. Normalize the state structure to avoid duplication and keep it flat for easier updates and lookups.

2. Use action constants: Define action types as constants to avoid typos and improve code consistency. This also makes it easier to identify and reference actions throughout your codebase.

3. Split reducers for modularity: As your application grows, consider splitting your reducers into smaller, more focused functions. This promotes modularity and makes your reducers easier to understand and maintain.

4. Leverage Redux DevTools: Take advantage of the Redux DevTools extension for debugging and time-travel capabilities. It provides a powerful set of tools to inspect and manipulate the state of your application.

Comparison with Other State Management Solutions

While Redux is a popular choice for state management, it‘s not the only option available. Here‘s a brief comparison with a couple of other solutions:

1. Redux vs MobX: MobX is another state management library that takes a different approach than Redux. It focuses on making state changes observable and automatically updating the relevant parts of the application. MobX has a more mutable and object-oriented style compared to Redux‘s immutable and functional approach.

2. Redux vs Context API: The Context API is a built-in feature of React that allows you to share data across components without explicitly passing props. While it can be used for state management, it‘s more suitable for small to medium-sized applications. Redux, on the other hand, provides a more structured and scalable approach to state management, especially for larger and more complex applications.

Conclusion

In this article, we explored the core concepts of Redux and learned how to implement it from scratch in just 24 lines of JavaScript. We saw how actions, reducers, and the store work together to provide a predictable and centralized state management solution.

Redux offers a powerful and flexible approach to managing state in JavaScript applications, promoting predictability, scalability, and maintainability. By following best practices and leveraging the tools and patterns provided by Redux, you can build robust and efficient applications.

Remember, Redux is just one piece of the puzzle. It works well in combination with other libraries and tools, such as React for building user interfaces and Redux Thunk or Redux Saga for handling asynchronous actions.

If you‘re new to Redux, I encourage you to dive deeper into the official documentation and explore the rich ecosystem of Redux-related libraries and tools. There‘s a wealth of resources available to help you master Redux and take your state management skills to the next level.

Thank you for reading, and happy coding!