What is React Redux? A Detailed Explanation

React Redux, along with Redux Toolkit, is a popular and powerful state management library for JavaScript applications. It provides an efficient and organised way to manage the state of your application and helps developers build scalable and maintainable code. It helps to handle data flow and state updates across components. In this blog you’ll get a detailed explanation of React Redux, covering its core concepts, benefits, and how it works. 

Table of Contents 

1) What is React Redux? 

2) Significance of React Redux 

3) The role of Redux in React applications 

4) The core concepts of React Redux 

5) Advanced techniques in React Redux 

6) Conclusion 

What is React Redux? 

React Redux is a State Management Library that seamlessly integrates with React - a JavaScript library for building User Interfaces (UIs). It serves as a predictable and efficient state container, enabling developers to manage and share the state of their applications.  

In a React application, components have their own state to manage data and handle user interactions. As the application grows in complexity and the number of components increases, managing and passing data between them can become challenging. It can lead to code that is hard to maintain. This is where React Redux comes into play.  

React Redux provides a centralized store, known as the Redux store, that holds the entire state of the application. This state management system is crucial for building scalable React applications, and understanding it is key when preparing for React Interview Questions. Instead of each component maintaining its own state, they can access the state from the Redux store. Any changes to the state are made by dispatching actions, which are plain JavaScript objects that describe the intention to modify the state.  

The Redux store then uses pure functions called reducers to handle these actions and update the state accordingly. These reducers ensure that the state modifications are predictable, and that the application follows a unidirectional flow of data.  

Significance of React Redux 

React Redux offers several key benefits that make it an essential tool for developing scalable and maintainable applications. Following are the features provided by React Redux: 

1) Centralised State Management: With React Redux, all components can access the same state from the centralised Redux store. This centralisation eliminates the need for complex data passing between components and ensures that the application's data remains consistent across the entire app.  

2) Predictable state changes: By following the principles of Redux, React Redux enforces a strict unidirectional data flow. Actions are dispatched to modify the state, and reducers handle these actions to update the state immutably. This predictability simplifies debugging and makes it easier to reason about how the application's state changes over time.  

3) Efficient rendering: React Redux optimises component rendering by using a concept called "selectors." Selectors are functions that compute derived data from the Redux state. By utilising selectors, components can efficiently access only the data they need, avoiding unnecessary re-renders and improving overall performance. 

4) Middleware support: Redux middleware allows developers to extend Redux's capabilities and add extra functionality to the dispatch process. Middleware can be used for tasks such as logging, handling asynchronous actions, and more. Popular middleware, like Redux-Thunk and Redux-Saga, enable seamless integration of asynchronous logic within Redux. 

5) Large ecosystem and community: React Redux benefits from a large and active community. Numerous resources, tutorials, and libraries are available to help developers understand and effectively use React Redux in their projects. This supportive community ensures that developers can find solutions to common problems and stay updated with best practices. 

The role of Redux in React applications  

Redux plays a crucial role in React applications by providing a predictable and efficient State Management solution. As React applications grow in complexity and size, managing the state becomes more challenging. This is where Redux steps in to simplify the process.  

Understanding State Management 

State Management refers to how an application handles and maintains data throughout its lifecycle. In a React application, each component can have its own state to manage data, specific to that component. However, as the application grows, passing data between multiple components and keeping everything in sync becomes cumbersome and error-prone.  

Redux addresses this challenge by introducing a centralised store that holds the entire state of the application. This means that all data is kept in a single location, making it easier to access and modify the state from any component without the need for complex data flow between components.  

Redux principles 

Redux follows three fundamental principles that guide its behaviour and ensure a robust State Management process: 
 

1) Single source of truth: The "Single Source of Truth" principle means that the entire state of the application is stored in a single JavaScript object called the Redux store. This store represents the sole source of data for the entire application. Having a single source of truth makes the state more predictable and easier to manage.  

With all data stored centrally, there is no ambiguity about where the state resides. With this, developers can quickly inspect and understand the application's data at any point in time. This simplifies debugging and ensures consistent behaviour across all components.  

2) Unidirectional data flow: Redux enforces a strict unidirectional data flow, meaning that data flows in one direction only. Actions are dispatched to the Redux store to indicate a specific intention, such as updating data or triggering an event. The store then uses reducers to handle these actions and update the state accordingly.  

The unidirectional data flow ensures that changes to the state are predictable and traceable. As actions flow through reducers, the state is updated immutably, preserving the previous state and making it easier to understand how and when changes occur.  

3) State is read-only: In Redux, the state is read-only. It means that components cannot directly modify the state in the store. Instead, components dispatch actions to the store to request state changes. The reducers, as pure functions, handle these actions and return a new state object, leaving the original state untouched.  

By keeping the state read-only, Redux ensures that changes to the state are explicit and controlled. This helps prevent accidental state mutations, which can lead to unexpected behaviour in the application. 

The core concepts of React Redux 

React Redux is built upon a set of core concepts that form the foundation of its State Management Architecture. Understanding these concepts is essential for effectively using React Redux in your applications. Here are the four core concepts of React Redux:  

Actions 

Actions are plain JavaScript objects that represent an intention to change the state of the application. They are the only source of information for the Redux store that conveys what happened in the application. An action typically contains a ‘type’ property that describes the type of action and any additional data necessary for the state update. 

For example, in a simple counter application, the action to perform counter increment would look like this: 

const incrementCounter = () => { 

  return { type: 'INCREMENT' }; 

}; 

Actions are created by action creators, which are functions that return actions. Action creators provide a convenient way to encapsulate the logic of creating actions and can also be used to handle more complex actions, such as asynchronous API calls. 

Reducers 

Reducers are pure functions responsible for handling actions and updating the state based on the type of action. A reducer takes the current state and an action as arguments and returns a new state that reflects the changes triggered by the action.  

Reducers must always return a new state object and never modify the existing state directly. This immutability ensures that the state changes are predictable, enabling efficient rendering and State Management.  

Here's a simple example of a reducer for our counter application: 

const counterReducer = (state = 0, action) => { 

  switch (action.type) { 

    case 'INCREMENT': 

      return state + 1; 

    default: 

      return state; 

  } 

}; 

The ‘counterReducer’ takes the current state (defaulting to 0 if no state is provided) and increases it by 1 when the 'INCREMENT' action is dispatched. For any other action type, the reducer returns the current state unchanged. 

Store 

The Redux store is a JavaScript object that holds the application's entire state. It is created using the ‘createStore’ function from the Redux library and is responsible for managing the state and handling actions dispatched by the components. The store provides three essential functions:  

1) ‘getState() ’: Returns the current state of the application. 

2) ‘dispatch(action)’: Dispatches an action to the store, triggering a state update. 

3) ‘subscribe(listener)’: Registers a listener function that is called whenever the state in the store changes. 

The store is the central piece of Redux and serves as the single source of truth for the entire application's state.  

Middleware 

Middleware in Redux provides a way to extend the store's capabilities and add extra functionality to the dispatch process. It sits between dispatching an action and the moment it reaches the reducer, intercepting actions and allowing developers to apply additional logic or side effects.  

Middleware is useful for handling asynchronous actions, logging, crash reporting, and more. Popular middleware like ‘Redux-Thunk’ and ‘Redux-Saga’ are commonly used to manage asynchronous behaviour in Redux applications. 

Advanced techniques in React Redux 

React Redux provides developers with a set of advanced techniques that can enhance the State Management process. They can also improve the overall efficiency and performance of the applications. These techniques go beyond the core concepts of React Redux and allow developers to handle complex scenarios and optimise their Redux-powered applications. Let's explore some of these advanced techniques:  

Async actions 

Asynchronous actions involve tasks like making API calls or handling side effects. While Redux handles synchronous actions seamlessly, handling asynchronous actions requires additional middleware. Redux provides various middleware libraries like ‘Redux-Thunk’, ‘Redux-Saga’, and ‘Redux-Observable’ to manage async operations. 

The ‘Redux-Thunk’ is a popular choice for handling asynchronous actions. It allows action creators to return functions instead of plain objects. These functions can dispatch multiple actions and perform asynchronous operations before dispatching the final action to update the state. 

Want to reduce component logic, refer to our blog on Higher Order Component in React

Redux DevTools 

Redux DevTools is an essential tool for developers working with React Redux applications. It is a browser extension that provides a powerful interface for inspecting, monitoring, and debugging the state changes in a Redux store.  

With Redux DevTools, developers can view the entire history of dispatched actions, replay actions, and even export and import states for easier debugging across sessions. It also allows developers to move backward and forward through state changes to identify bugs or understand the application's behaviour at different points in time.  

Immutability 

Immutability is a fundamental concept in Redux. Ensuring that the state remains immutable throughout the application prevents accidental mutations and improves the predictability of state updates.  

Immutable updates involve creating new objects or arrays instead of modifying existing ones. Libraries like ‘immutable.js’ provide immutable data structures and utilities that can be integrated with Redux to ensure that the state is updated in an immutable manner. By enforcing immutability, Redux makes it easier to understand how and when the state changes, avoiding bugs related to shared mutable states. 

Selectors 

Selectors are functions that compute data, derived from the Redux state. They act as an interface between the state and the components, allowing components to access specific parts of the state without knowledge of its structure.  

Selectors play a crucial role in optimising rendering performance. By memorising the results of selectors, components can efficiently access the data they need, avoiding unnecessary re-renders when unrelated parts of the state change.

Conclusion 

React Redux's unidirectional data flow, support for middleware, and efficient rendering make it a robust choice for State Management in modern web development. Embracing React Redux empowers developers to create sophisticated and data-driven User Interfaces, making it a vital addition to any React developer's toolkit. By centralizing the state in a Redux store and following Redux principles, developers can build scalable, efficient, and maintainable web applications, as demonstrated in various React JS Projects. 

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