React Redux Tutorial - A Beginner's Guide
Updated on 14th Dec, 23 9.1K Views

For rookie learners, this tutorial offers detailed and complete instructions on comprehending and executing React Redux.

Check out this React JS Full Course video to learn more about its concepts:

What is Redux?

Redux is a predictable state container for JavaScript apps. It enables you to create apps that operate consistently across client, server, and native platforms and are simple to test.

Redux is a library, not a framework. It doesn’t dictate how your app should be structured, but it does provide a way to manage the state of your app consistently and predictably.

Why Redux with React?

Redux is an exceptional state management library that perfectly balances React and supports creating large-scale, complex applications. Redux allows you to manage and update your data effectively by giving you a single location for your application’s state. Consolidating state management enables seamless state transitions and improves control. 

Here are some of the specific benefits of using Redux with React:

  • Centralized state: One store for all state, reducing complexity and improving performance.
  • Predictable state updates: State can only be updated by dispatching actions, making it easier to reason about and debug.
  • Performance: Avoids unnecessary re-renders, improving performance, especially for large applications.
  • Developer experience: Hot reloading and time travel debugging make developing and debugging applications easier.
  • Modularity: Encourages breaking the state into small, manageable pieces.
  • Scalability: Well-suited for large, complex applications.

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Three Principles of Redux

Principles of Redux
  • Single Source of Truth
    Creating universal apps becomes easy because you can serialize and hydrate the server’s state into the client without additional coding. Debugging and inspecting an application are simplified with a single state tree. It also allows you to persist in your app’s state during development for a faster cycle. Implementing traditionally challenging functionalities like Undo/Redo becomes effortless when all the state is stored in a single tree.
console.log(store.getState());

Output:
{
  visibilityFilter: 'SHOW_ALL',
  todos: [
    {
      text: 'Consider using Redux',
      completed: true,
    },
    {
      text: 'Keep all state in a single tree',
      completed: false
    }
  ]
}
  • Changes are Made with Pure Functions
    Pure functions called reducers receive the previous state and an action and then produce the next state. It is important to create and return new state objects rather than modify the existing state. Initially, you can begin with a single reducer, but as your application expands, you can separate it into smaller reducers that handle distinct sections of the state structure. Since reducers are essential functions, you have the ability to control their invocation order, provide additional data, or even create reusable reducers for common operations like pagination.
function visibilityFilter(state = 'SHOW_ALL', action) {
  switch (action.type) {
    case 'SET_VISIBILITY_FILTER':
      return action.filter;
    default:
      return state;
  }
}

function todos(state = [], action) {
  switch (action.type) {
    case 'ADD_TODO':
      return [
        ...state,
        {
          text: action.text,
          completed: false
        }
      ];
    case 'COMPLETE_TODO':
      return state.map((todo, index) => {
        if (index === action.index) {
          return {
            ...todo,
            completed: true
          };
        }
        return todo;
      });
    default:
      return state;
  }
}

import { combineReducers, createStore } from 'redux';

const rootReducer = combineReducers({ visibilityFilter, todos });
const store = createStore(rootReducer);

export default store;

By adhering to the principle of using pure functions, Redux ensures that state modifications are explicit, predictable, and maintainable. It promotes a disciplined approach to state management and helps developers build applications that are easier to understand, debug, and extend.

  • State is Read-Only
    This guarantee ensures that the state will never be written directly by either the views or the network callbacks. Instead, they communicate their intention to transform the state. By centralizing all changes and ensuring they occur one by one in a strict order, there is no need to be cautious of subtle race conditions. Actions, being simple objects, can be logged, serialized, stored, and easily replayed later for debugging or testing purposes.
// Define action types
const COMPLETE_TODO = 'COMPLETE_TODO';
const SET_VISIBILITY_FILTER = 'SET_VISIBILITY_FILTER';

// Define action creators
function completeTodo(index) {
  return {
    type: COMPLETE_TODO,
    index: index
  };
}

function setVisibilityFilter(filter) {
  return {
    type: SET_VISIBILITY_FILTER,
    filter: filter
  };
}

// Dispatch actions
store.dispatch(completeTodo(1));
store.dispatch(setVisibilityFilter('SHOW_COMPLETED'));

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Pros and Cons of Redux

Redux is a widely used state management library that offers several benefits for developing complex JavaScript applications. However, it also comes with certain drawbacks. Let’s explore the pros and cons of Redux in detail:

Pros of Redux

  1. Simplified State Management: Redux provides a centralized store that simplifies state management in large-scale applications. With Redux, components can access and modify the application state without the need for complex data flow patterns or prop drilling. This centralized approach streamlines the process of handling the state, making it easier to reason about and maintain.
  2. Predictable Data Flow: Redux follows a unidirectional data flow, ensuring that data changes are predictable and easier to understand. Actions are dispatched to modify the state, and reducers handle these actions to produce a new state. This predictable flow makes it easier to trace and debug state-related issues, enhancing the overall stability of the application.
  3. Enhanced Code Organization and Maintainability: By separating the state management logic from the components, Redux improves code organization and maintainability. With Redux, components become more focused on rendering UI based on the provided state, while the state management logic resides in reducers. This separation of concerns promotes cleaner and more maintainable code, making it easier to add new features or refactor existing ones.
  4. Easy Debugging and Testing: Redux simplifies debugging and testing. The predictable data flow and immutability of the state make it easier to trace and understand how state changes occur. Additionally, since reducers are pure functions, they are easier to test as they don’t have any side effects. Unit tests can be written to verify the behavior of reducers and ensure that state modifications are handled correctly.

Cons of Redux

  1. Additional Complexity for Small or Simple Applications: Redux introduces additional complexity, especially for small or simple applications. The setup and configuration required to integrate Redux into a project might be excessive for applications with limited state management needs. In such cases, using a local component state might be a simpler and more lightweight solution.
  2. Steeper Learning Curve: Learning Redux and understanding its concepts, such as actions, reducers, and the unidirectional data flow, can be challenging for developers who are new to the library. It requires a shift in mindset and a solid understanding of functional programming principles. However, once the core concepts are grasped, Redux can greatly benefit the development process.
  3. Requires Writing More Code: Implementing Redux requires writing additional code compared to managing state locally within components. Actions, reducers, and store configuration all require code to be written and maintained. While Redux provides a powerful state management solution, it does come with an overhead in terms of development effort.

It’s important to consider these pros and cons when deciding whether to adopt Redux for a project. Redux shines in larger applications with complex state management requirements, where the benefits of a centralized state and predictable data flow outweigh the additional complexity. However, for smaller or simpler applications, using a local component state might be a more lightweight and straightforward approach.

Components of Redux

Components of Redux


Redux consists of three key components that work together to enable efficient state management in JavaScript applications. These components are the store, actions, and reducers. Understanding how these components interact is crucial to effectively utilizing Redux.

Reducers

Reducers are considered pure functions that specify how the state should change in response to dispatched actions. They take in the current state and the dispatched action as arguments, and return a completely new state object based on the changes described in the action. The original state is not modified, ensuring immutability.

A reducer typically follows the switch statement pattern, where the action type is used to determine how the state should be updated. Each case within the switch statement handles a specific action type and returns the updated portion of the state.

Here’s an example of a reducer that handles the ‘ADD_TO_CART’ action:

function cartReducer(state = [], action) {
  switch (action.type) {
    case 'ADD_TO_CART':
      return [...state, action.payload];
    default:
      return state;
  }
}

Reducers are combined using the `combineReducers` function provided by Redux. This allows multiple reducers to handle different parts of the state and be composed together to form the complete state tree.

When an action is dispatched, Redux ensures that the relevant reducers are called with the current state and the action, and the resulting new state is stored in the store. Components can then access the updated state from the store and re-render accordingly.

Store

The store is the central component of Redux. It serves as a container that holds the application state. The store is created using the `createStore` function provided by the Redux library. The store is responsible for managing the state and providing methods for accessing and updating its state as needed.

The store holds the current state of the application, which is represented as a single JavaScript object. Components can access the state by subscribing to the store and retrieving the data they need. The store also allows components to dispatch actions to modify the state.

Actions

Actions are referred to as plain JavaScript objects that describe an event or an intention to modify the state. They are dispatched by components to trigger state changes. Actions contain a `type` field, which is a string that identifies the action type, and can also include additional data as needed.

For example, an action for adding a new item to a shopping cart might look like this:

{
  type: 'ADD_TO_CART',
  payload: { productId: 123, quantity: 1 }
}

Actions are typically defined as functions called action creators, which return the action objects. Action creators provide a convenient way to encapsulate the creation of actions with predefined types and data.

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React With Redux

React and Redux are often used together to create robust and scalable applications. React handles the UI rendering and component hierarchy, while Redux provides a centralized state management solution. Let’s explore how React integrates with Redux and the key steps involved.

Setting Up Redux in a React Application

To set up Redux in a React application, several steps need to be followed:

1. Install the Redux and React-Redux packages.

npm install redux react-redux

2. Create a store.

import { createStore } from "redux";

const store = createStore(
  reducer,
  initialState,
  middleware
);

3. Create a reducer.

const reducer = (state, action) => {
  switch (action.type) {
    case "ADD_ITEM":
      return {
        ...state,
        items: [...state.items, action.payload],
      };
    default:
      return state;
  }
};

4. Create an action.

export const ADD_ITEM = "ADD_ITEM";

export const addItem = (payload) => ({
  type: ADD_ITEM,
  payload,
});

5. Connect your components to the Redux store.

import { connect } from "react-redux";

const MyComponent = ({ state, dispatch }) => {
  const items = state.items;
  const handleAddItem = () => {
    dispatch(addItem("New item"));
  };
  return (
    <div>
      <ul>
        {items.map((item) => (
          <li key={item}>{item}</li>
        ))}
      </ul>
      <button onClick={handleAddItem}>Add Item</button>
    </div>
  );
};

const mapStateToProps = (state) => ({
  state,
});

const mapDispatchToProps = (dispatch) => ({
  dispatch,
});

export default connect(mapStateToProps, mapDispatchToProps)(MyComponent);

Connecting React Components to Redux

To connect React components to Redux and access the state and dispatch actions, the `connect` function from the `react-redux` library is used. This function creates a higher-order component (HOC) that connects the component to the Redux store.

1. Import the connect function from react-redux.

import { connect } from "react-redux";

2. Create a function that maps the Redux state to props for your component. This function is called mapStateToProps.

const mapStateToProps = (state) => ({
  // The state of your component will be available here.
});

3. Create a function that maps the Redux actions to props for your component. This function is called mapDispatchToProps.

const mapDispatchToProps = (dispatch) => ({
  // The dispatch function will be available here.
});

4. Call the connect function, passing in the mapStateToProps and mapDispatchToProps functions.

const MyComponent = connect(mapStateToProps, mapDispatchToProps)(MyComponent);

5. Render your component as you normally would.

<MyComponent />

By following these steps, React components can efficiently connect to the Redux store, access the state, and dispatch actions to modify the state. This integration enables a powerful and predictable state management solution in React applications.

Conclusion

Redux simplifies state management in React by introducing a centralized store and predictable data flow. Its principles and components enhance code organization and maintainability while improving debugging and testing capabilities. Although it may not be necessary for small applications, it is beneficial for complex state management needs. By properly setting it up, developers can create cleaner, more scalable code and deliver high-quality software solutions.

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