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Table of contents
1.
Introduction
2.
Redux Interview Questions and Answers For Freshers
2.1.
1. What is Redux?
2.2.
2. What is React?
2.3.
3. Give some advantages of using Redux.
2.4.
4. Is the state in Redux mutable or immutable?
2.5.
5. What is flux?
2.6.
6. What is meant by Component Driven Development?
2.7.
7. Name some common libraries that complement Redux.
2.8.
8. What are the key differences between Redux and Flux?
2.9.
9. What do you mean by Redux Form?
2.10.
10. What are actions in Redux?
2.11.
11. What is the role of a Reducer in Redux?
2.12.
12. Mention key disadvantages of Redux.
2.13.
13. Should all component states be stored in the Redux store?
2.14.
14. Important differences between mapStateToProps() and mapDispatchToProps() ?
3.
Redux Interview Questions and Answers for Intermediate
3.1.
15. How can you explain the Hooks API in Redux?
3.2.
16. How does Redux achieve predictability?
3.3.
17. What do you understand by constants in Redux?
3.4.
18. What is Store in Redux?
3.5.
19. What are the common Store methods in Redux?
3.6.
20. Explain workflow features in Redux.
3.7.
21. What is redux-saga?
3.8.
22. Explain Redux Selectors.
3.9.
23. What are the core principles of Redux?
3.10.
24. What do you understand by Redux Thunk?
3.11.
25. What is the purpose of the connect function in React-Redux?
3.12.
26. How would you define an action within Redux's architecture?
3.13.
27. Could you provide an example that demonstrates the utilization of actions within Redux's architecture? 
3.14.
28. Explain the purpose of the redux-observable library in Redux.
4.
Redux Interview Questions and Answers for Experienced
4.1.
29. What do you mean by a "store" in Redux?
4.2.
30. How to structure your top-level directories in Redux?
4.3.
31. What is meant by Virtual-DOM?
4.4.
32.  Differentiate between Relay & Redux.
4.5.
33. Can Redux and RxJS work together?
4.6.
34. What are the major features of React Forms?
4.7.
35. Can We access a redux store outside a react component?
4.8.
36. What do you understand about Redux Toolkit?
4.9.
37.  What is Redux DevTools?
4.10.
38. What is the use of the mapStateToProps() method?
4.11.
39. How can you prevent prop drilling and what exactly is it?
4.12.
40. What do you understand by Redux in React? 
5.
Conclusion
Last Updated: Jun 12, 2024
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Top Interview Questions and Answers for Redux in 2024

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Introduction

Redux is an open-source Javascript Library. It acts like a central store to store the various state of an application. It is used for managing and centralizing the state of an application. We can refer to Redux as a State Container. 

This blog covers a set of redux interview questions which will give you a brief understanding of what questions are asked in such interviews and prepare you for the same. 

Interview Questions for Redux

Redux Interview Questions and Answers For Freshers

1. What is Redux?

Redux is an open-source Javascript Library. It acts like a central store to store the various state of an application. It is used for managing and centralizing the state of an application. We can refer to Redux as a State Container. It is commonly used in integration with various other javascript libraries such as React or Angular.

2. What is React?

React is a free and open-source javascript library developed by Facebook and used in the front-end development of applications. It makes it easier to build the user interfaces of the applications. It can often be used in integration with other libraries, such as Redux.

3. Give some advantages of using Redux.

Redux is an open-source Javascript Library. It acts like a central store to store the various state of an application. Several advantages of using Redux are mentioned below.

  • Redux acts like a Centralised Store for storing all the states of the application.
     
  • It can be easily integrated with other javascript libraries such as React, Angular, etc.
     
  • The use of pure functions makes it easier to test the application and ensure safety features. 

4. Is the state in Redux mutable or immutable?

Redux supports an immutable state. This implies that the status cannot be directly changed. Any modifications to the state must instead be made by establishing a new state object and applying the modifications to it.

Immutable state is necessary for Redux for a number of reasons. It makes it simpler to reason about the application's state. When the state is immutable, it is always evident what the application's present state is. This makes finding flaws and debugging simpler.

5. What is flux?

Flux is similar to the Model View Controller design architecture. Flux is an architecture used in React based on the unidirectional data flow concept. Flux involves Actions, Stores, The Dispatcher, and Views.

6. What is meant by Component Driven Development?

Redux employs the software development process known as component-driven development (CDD), which manages an application's state using components. Each component maintains its own state, and actions are dispatched to alter the state.

Compared to conventional state management strategies, CDD in Redux has several benefits. First of all, it makes it simpler to think about the application's current state. It is obvious what each component is in charge of when components control the state. This makes finding flaws and debugging simpler.

7. Name some common libraries that complement Redux.

Redux can be easily used in the integration with other javascript libraries. Some of them include:

  • React
     
  • Angular
     

Both of these libraries are used for building user interfaces of applications.

8. What are the key differences between Redux and Flux?

In flux, there are multiple stores to store the application states, whereas Redux stores the various states in a single store. Redux provides a set of tools called devtools for debugging; the flux doesn’t provide such tools.

9. What do you mean by Redux Form?

Redux Forms allow a form in React to comprehensively use Redux to store all of its states in the store. They are available in both React and Redux. Redux forms are easily compatible with several UI frameworks such as Material UI, React Widgets, React Bootstrap, etc.

10. What are actions in Redux?

Actions are simple JavaScript Objects containing information for the store. They consist of a type field and other data or information fields(payload). The type field specifies which action to perform. The payload(data or information field) describes the action.

11. What is the role of a Reducer in Redux?

Reducers form special functions which take the current state and return the next state. The role of a reducer is to specify how the state of the application should change in response to actions.

12. Mention key disadvantages of Redux.

Some of the key disadvantages are:

  • Redux adds a significant amount of complexity to your application. 
     
  • Redux can be time-consuming as it requires more inputs of the boilerplate code to begin writing.
     

13. Should all component states be stored in the Redux store?

Not all the component states should be stored in the redux store. We should store only those states which are shared across multiple components in Redux.

14. Important differences between mapStateToProps() and mapDispatchToProps() ?

mpStateToProps() is used to map the Redux state to component props, while mapDispatchToProps() is used to map Redux actions to component props for dispatching.

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Redux Interview Questions and Answers for Intermediate

15. How can you explain the Hooks API in Redux?

Redux has a set of functions called the Hooks API that let you connect Redux with other function components. You may now design more compact, reusable components with React's function components feature.

You can use a variety of hooks provided by the Hooks API to dispatch actions, manage state, and access the Redux store. Some of the hooks that are most frequently used include:

  • useSelector: With this hook, you can pick a state component from the Redux store.
     
  • useDispatch: The useDispatch hook is used to send an action to the Redux store.
     
  • useState: The useState hook is used to control the state of a function component.

16. How does Redux achieve predictability?

Redux achieves predictability by using the following principles:

  • Single source of truth: The Redux store keeps the application's state. This makes it simple to monitor state changes and confirm that all components use the same information.
     
  • Reducers: Reducers are operations used to change the application's state. Since reducers are pure functions, they consistently produce the same result for the same input.
     
  • Immutability: Since the application's immutable state cannot be altered directly. Instead, a new state object is created to make modifications to the state. As a result, analysing the status of the programme and avoiding errors is made simpler.

17. What do you understand by constants in Redux?

Constants define action types that are string values describing the type of action being performed. They distinguish between different actions in the reducer and help to prevent typos and other mistakes that can lead to bugs. Constants are typically defined as named variables. 

18. What is Store in Redux?

A Store in Redux can be referred to as the state container, which evidently, holds the application's state. It is an immutable object tree holding the whole state tree of the application. We can create a store object in redux using the createStore() function.

19. What are the common Store methods in Redux?

A Store in Redux can be referred to as the state container, which evidently, holds the state of the application. Various store methods are mentioned below:

  • createStore(): This method creates a store in redux. 
     
  • dispatch(action): This method changes the state by dispatching the actions.
     
  • getState(): This method is used to determine the store's current state in redux.

20. Explain workflow features in Redux.

There are four workflow features in Redux.

  1. Reset: to reset the state of the store in Redux.
     
  2. Revert: to roll back to the last committed state.
     
  3. Sweep: to delete all the disabled actions fired by mistake
     
  4. Commit: to make the current state the initial state

21. What is redux-saga?

Redux Saga is a middleware for Redux. Redux-Saga easily handles side effects such as asynchronous requests or logging in to a React-Redux application. Side effects are operations that impact the state of the application outside of the normal flow of control. It uses a mechanism called generators to manage the flow of control in your side-effect logic. Generators are ideal for handling asynchronous operations that can be paused and resumed multiple times.

22. Explain Redux Selectors.

Redux selectors are functions used to extract data from the Redux store. They take the stored state as an argument. After Extracting the state, the selectors can perform transformations on that data, such as filtering, mapping, or aggregating, before passing it to a component.

23. What are the core principles of Redux?

There are three core principles of Redux

  1. Single Source of Truth - The global state of the application is stored in a single store, in an object tree.
     
  2. The State is read-only - We can change the state by emitting an action or object describing what happened. The state itself is considered read-only.
     
  3. Changes are made with pure functions - Reducers form special functions which take the current state and return the next state. Reducer functions should be pure and do nothing more than return the next state.

24. What do you understand by Redux Thunk?

Redux Thunk is a popular middleware for the Redux state management library. It provides a way to handle asynchronous logic inside action creators in a Redux application. The middleware allows for actions to be dispatched, enabling you to write more complex logic that involves asynchronous operations. With Redux Thunk, you can write action creators that perform asynchronous logic and then dispatch additional actions based on the results.

25. What is the purpose of the connect function in React-Redux?

The connect function in React-Redux connects a react component to the redux store. It provides the data from the store to a component and then dispatches actions to the store so that the component can interact with the store and trigger changes in the state.

26. How would you define an action within Redux's architecture?

It is a javascript object that contains a type field. We can also think of action within redux's architecture as an event or state that tells us about all the happenings in the architecture.

27. Could you provide an example that demonstrates the utilization of actions within Redux's architecture? 

An example that demonstrates the utilization of action within redux's architecture can be an increment counter. Let us look at the code snippet of the increment counter below.

const incrementCounterAction = {
  type: 'INCREMENT_COUNTER'
};

28. Explain the purpose of the redux-observable library in Redux.

redux-observable is a middleware library for Redux. It uses reactive programming to handle complex asynchronous logic simply and elegantly. It allows developers to manage side effects such as API calls, data fetching, and other time-based events in a unified and centralized manner while still adhering to the principles of the Redux architecture.

Redux Interview Questions and Answers for Experienced

29. What do you mean by a "store" in Redux?

The store is a container that has all the information about the complete state tree of an application. It can also be called a javascript object that manages and contain the application state. The store should always be considered as a single source of truth for all the states of an application.

30. How to structure your top-level directories in Redux?

The top-level directories in Redux are structured in the following way. 

Components

This directory has presentational components. These components render the UI and receive props from their parent components.

Containers

This directory contains the connected components (smart components) connected to the Redux store and provides the data and actions from the store to the presentational components.

Actions

This directory contains the action creators and the action types used to dispatch actions to the store.

Reducers

This directory contains the reducers responsible for updating the store's state in response to actions being dispatched.

Store

This directory contains the store configuration and any middleware used in the application.

31. What is meant by Virtual-DOM?

DOM refers to Document Object Model. The Virtual DOM (VDOM) efficiently updates the user interface of a web page. It is an in-memory representation of the actual DOM (Document Object Model), which is the hierarchical structure of a web page as seen by the browser.

When changes are made to the state of a web page, the Virtual DOM calculates the differences between the current state and the new state. It then updates only the parts of the actual DOM that need to be changed rather than re-rendering the entire page.

32.  Differentiate between Relay & Redux.

Redux is an open-source Javascript Library. It acts like a central store to store the various state of an application. Redux manages all the states of the application. Relay, on the other hand, manages the state originating from the server. Relay performs caching and optimization on data, whereas Redux does not handle data fetching. Both have a single store for storing the states and can be easily integrated with React library.

33. Can Redux and RxJS work together?

RxJS is a javascript library for reactive programming and is used to complete asynchronous activities. Redux is an open-source Javascript Library. It acts like a central store to store the various state of an application. In some cases, we use Redux and RxJS together.  For example, to manage application state and handle asynchronous events in a React application. Redux manages the centralized store in these cases, and RxJS handles the asynchronous data streams and events.

34. What are the major features of React Forms?

Some major features of the Redux Forms are:

  • Redux Forms provide built-in support for form validation, allowing you to define validation rules for your form fields and display error messages to the user.
     
  • Redux Form provides a comprehensive way to submit forms, making it easy to handle form submissions in your application.
     
  • Storing field values in the Redux store is one of the key benefits of using Redux Form.

35. Can We access a redux store outside a react component?

Yes, we can access the redux store outside a react component. To access a redux store outside a react component, export the store from the module where it has been created using createStore(). The store created by Redux can be accessed from anywhere in your application by importing the store and the getState method.

An example is shown below.

store = createStore(reducer);
export default store;

36. What do you understand about Redux Toolkit?

Redux Toolkit is a popular library for Redux that provides a more efficient and easier way to write Redux logic. It provides a set of utilities and conventions that make it easier to write high-quality Redux code and can help you avoid some of the common pitfalls of using Redux.

Some of the key features of Redux Toolkit include

  • Automated handling of action creators and action types
     
  • Simplified handling of asynchronous logic with the createSlice function
     
  • Improved store setup with the configureStore function

37.  What is Redux DevTools?

Redux DevTools is a popular open-souce extension or a package (It can be used as both) that provides a debugging platform for applications. It provides the features of time-travel debugging and live editing. With devtools, we can inspect the state and action payload and even re-evaluate the staged action after changing the reducer code.

38. What is the use of the mapStateToProps() method?

mapStateToProps() specifies which pieces of the state from the store should be passed down as props to a particular component. This function takes the store's current state as an argument and returns an object that maps the state of the component to the props. The method connects the Redux state to the React component’s props.

39. How can you prevent prop drilling and what exactly is it?

Prop drilling is the process of transmitting data across a chain of intermediary components from one component to another. This may make it more challenging to test and harder to interpret and maintain code.
Several measures can be used to avoid prop drilling:

Use a context provider: Context providers allow components to communicate without passing data through props.


Use functional components: React's latest feature, functional components, makes it simpler to design reusable components.


Use composition: Combining smaller elements to produce larger ones is the practise of composition. By doing this, the amount of prop drilling required may be decreased.

40. What do you understand by Redux in React? 

Reduct is commonly used with React to build User Interfaces for scalable applications. The React-Redux library provides tools for connecting React Components to Redux Store. Redux in React allows the react components to read data from the Store and update the data by dispatching Actions. Redux makes it easier to scale the applications by managing the state of the application at all times using unidirectional data flow architecture.

Conclusion

We discussed the redux interview questions (easy, medium, and hard). We hope these questions helped you enhance your knowledge. Refer to the above redux interview questions as the most asked questions in any redux related interview.

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