What are React Interview Questions: Top 20 React Interview Questions

If you want to become a front-end innovator and are getting ready for interviews, Everyone seems to use the word “react” all the time. This React interview questions lesson is perfect if you are searching for a job and are ready for an interview. React is now the most popular front-end technology, and more and more businesses are starting to use it. Here is a complete list of the most frequently asked React interview questions, which range from easy to hard. You should read this blog post on the Top 20 React Interview Questions.

Choosing the best technology to make a website or app takes more work. React, a JavaScript framework has been getting more popular faster than any other. JavaScript tools are slowly getting more popular in the market, while the number of people wanting to get a React certification is skyrocketing. React is very popular among front-end developers because it is easy to learn, can be reused, and has a clear separation of concerns.

What is React?

A free JavaScript library called React can be used to make interactive user interfaces. Facebook created it, and they and a group of third-party developers and companies that care about its safety keep it running. React makes making complex and responsive user interfaces easier by letting programmers make UI components that can be used more than once and handle the state of their application.

Features and Significance of React

MVC is often used as a shorthand for Model View Controller.

1. React’s view rendering is faster because it uses virtual DOM. A “virtual DOM” is a copy of the original Document Object Model stored in a computer. When a react app’s data changes, a new virtual DOM is built. Making a virtual DOM is faster than waiting for the browser to render the user interface. In this way, the app works better because of the virtual DOM.
2. React is much easier to learn than other frameworks like Angular. Even if you only know the basics of JavaScript, you can use React to start making sophisticated online apps.
3. Using React, web designers can make appealing user interfaces that are also good for search engines. It makes server-side rendering possible, which improves the SEO of an app.
4. Because React is built modularly and uses a component-based architecture, it is easy to make and reuse software building blocks. Components are code that can be used more than once and can work independently. These parts can be used in other programs that have similar goals. Reusing features speeds up the development process.
5. Because React has an extensive library ecosystem, you can build apps with the tools, libraries, and architecture that work best for you.

What are the Limitations of React?

• Since React is just a library, it is not a full-fledged framework.
• React has many parts; it will take time to understand how they all work together.
• Beginner programmers need help figuring out how to use React.
• Because it will use inline templating and JSX, the code could get more complicated.

Meaning of React Interview Questions

React interview questions are the kinds of questions that are asked during an interview for a job that requires using the React JavaScript library. The questions are meant to test how well a candidate knows and understands React and its different features and how well they can use React to make user interfaces that are dynamic and scalable.

The questions can be about many different things, like parts, state management, performance, and other similar items. During an interview, the questions asked will depend on the position being interviewed for and what the job entails. But some everyday things that might be discussed are React components, state management with React, React performance, and using React with other libraries and tools like Redux and Webpack.

React interview questions aim to help the interviewer determine if a candidate has the knowledge, skills, and experience needed to use React to build high-quality user interfaces.

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Top 20 React Interview Questions:

1.Please explain what React is and how it helps.

React is the JavaScript library that is most often used to make user interfaces. It was created by Facebook and is still supported by them. Many companies and independent programmers now use it to make UIs that load quickly and respond well to what the user does.

The Virtual DOM is a concept that React uses to make rendering and updating components easy. React uses the Virtual DOM, a lightweight representation of the DOM that lives in memory, so the user interface doesn’t have to be re-rendered. Because updates can be made quickly and easily, this makes React is an excellent choice for creating complex and dynamic user interfaces. When it comes to making user interfaces, React not only has a strong and flexible architecture based on components, but it also has a very efficient way of handling updates. Components are what make up the parts of a React interface. They are the building blocks that allow designers to make parts that can be used in different situations. This makes building and maintaining complex interfaces easier and ensures that they will last for a long time.

2. How does React handle changes to its virtual Document Object Model (DOM), and why is this important?

React ensures updates are as fast as possible by only changing the parts of a user interface that have changed. We do this with a method called “reconciliation,” which creates a new digital DOM tree to stand in for a better user interface. React updates the DOM once it has figured out the fewest necessary changes. React uses a virtual DOM to describe to the user better how to change the real DOM. This makes upgrades go faster and adds more features.

3. Tell me about React components and how they can be used in a project.

Components made with React are the essential parts of a React application. They are separate UX parts that can be combined to create more complex UIs. Both class-based and functional components decide how the UI elements they stand for are laid out, how they work, and how they look.

4. What is the point of “state” when working with React?

In React, “state” means the data or variables that control how a component acts and how information is shown to the user. It’s an essential part of using React to build dynamic user interfaces. The state stores and manages data that changes over time, such as the current value of an input field, the shape of a toggle, or the data fetched from an API. The state can be changed by the component itself, unlike props, which can only be read and are passed from a parent to a child. The state of a component determines how it should look, so when the state changes, the component re-renders to show the new information. This lets React update the user interface quickly as the state changes over time. This makes it possible to create user interfaces that are dynamic and interactive.

5. What are the props and states in React?

Props and state are two crucial ideas in React used to manage data and change how components act. Props, short for “properties,” are values sent from parent to child components. Props can only be read, so the child component can’t change them. Props send data from the parent to child components and control how the user interface looks and works.

6. What does it look like to process user input with React?

When you make a controlled component in React to handle user input, it takes care of its state and gets updates as needed.

7. What does the render() method of React return, and what exactly does it do?

A React component’s render method gives back a tree of React elements that describe the user interface. Elements are the main focus of development because they are the building blocks of a React UI. They are simple JavaScript objects that tell how a UI element should look. A React element could define, among other things, a button, a text box, or a header.

 When the state or props of a component change, for example, the render method is called so that the component’s view can be updated. The render method must be pure, which means it can’t do anything unexpected and always gives the exact same output when given the same input.

8. Can you explain more about how and when the lifecycle functions of a React component are called?

React parts have several “lifecycle” methods that are called at different times, such as when the branch is created, changed, or destroyed. To make suitable, well-behaved components, you need to know what these methods are called and why they are used.

9. What happens inside the componentDidMount() method when a React component is mounted?

React calls the componentDidMount() approach after rendering to the DOM. This method is run once during the lifecycle of the part.

 React components are set up with the componentDidMount() method:

• Set up: Set the state, connect the event handlers, and get the data.
• Start asynchronous operations: to change the component’s state here, like getting data.
• Interact with the DOM: This method lets you change and get the values of elements. Use React’s state and props to control the component’s behavior instead of changing the DOM.
• Events: Here’s how to sign up.

The componentDidMount() method is called after the DOM has been drawn. The component and its children will be entirely removed and able to be moved around. This is helpful for third-party libraries that need to start up and need a DOM node.

10. Give an example of how you might use the conditional rendering feature of React.

Conditional rendering in React means rendering elements or components based on certain conditions. To render elements based on particular situations, you can use an if statement or a conditional operator, also called a ternary operator.

11. What is Redux?

Redux is a popular JavaScript tool for handling states used in many modern web apps. Even though it was made with React in mind, you can use it with any other JavaScript library or framework. In a web application, the term “state” refers to the data or variables that control how a component acts and how it shows itself to the user. Information like this could come from user input, queries sent over the network, or data stored locally.

12. What are the three main ideas that Redux follows?

• Everything an app needs to run is kept in a single object tree called the store, which is the official record of the app’s state. You can always know what’s happening with your app because everything is in one place.
• Write-only mode: Sending out actions is the only way to change the state. Actions are the things that happen inside the application, and simple objects represent them. This ensures that data only flows in one direction, and it also helps to keep the logic for updating the state and the logic for drawing the user interface completely separate.
• Changes are made with only functional code, and the state is changed based on user input with the help of reducers. A reducer is a purely available program that takes the current state and an action as inputs and returns a new form as output. Because of this, the state changes are easy to understand because they are both predetermined and have no signs.

13. How do you use React Router?

With React Router, a powerful routing module built on top of React, it’s easy to add new screens and workflows to an app. This makes sure that the URL always tells the truth about what the page is about. It can be used to make single-page web apps that have a consistent structure and way of working. The React Router application programming interface (API) is easy to use.

14. How do React’s events compare to those of other systems?

Changes have been made to the syntax of React elements when handling events: All React event handler names must use CamelCase rather than lowercase.

If you’re familiar with JS, you’ll know that JSX event handlers take the form of functions rather than strings.

15. Tell about Flux.

Flux is an architectural design paradigm that requires a one-way flow of data. This framework controls derived data and makes it easier for different parts to work together by using a unified Store as the ultimate source of truth for all data. All changes to data for the whole application must be made here. The app is more reliable and has fewer errors in flux.

16. Higher Order Components, or HOC, is a term, but what are these?

We can save time and effort by reusing component logic in a higher-order way, like with Higher Order Components. It’s a style that comes naturally from how React is put together. HOCs are unique parts that hold other positions inside. In other words, they will take any child component given to them wholly and dynamically ignore its behavior. HOC is a ‘pure’ component, in a sense.

17. How do you define pure components?

Pure components are the easiest and fastest to code. If a part only has a render, it can be changed (). These parts make it easier to understand the code and run faster.

18. How do you use React Router?

With React Router, a powerful routing module built on top of React, it’s easy to add new screens and workflows to an app. This makes sure that the URL always tells the truth about what the page is about. It can be used to make single-page web apps that have a consistent structure and way of working. The React Router application programming interface (API) is easy to use.

19. Why exactly does React need a Router?

If the user types in a URL that matches the path of a “route” set up in a Router, the Router will send the user to the URL set up for that Router. So, we must add a Router library to our program. This will let us make different routes, each of which will take us to a different view.

20. Show how a Render Prop can be used in React.

In React, a render prop can describe how a component acts. A render prop is a function that a member uses to decide what to render instead of sending data and behavior through its support. The “provider” component makes the render prop available, but the “consumer” component is the one that uses it. This method makes it easier for parts to be changed and used again.

These questions determine how well a newcomer understands React’s most important ideas. If a beginner can’t get the basics of React, they might not be able to use the framework well in a production setting.

What is SPFX? How it is connected to React.

SharePoint Framework, or SPFx, is a web framework used to build and deliver SharePoint add-ons in both the cloud and on-premises environments. It lets programmers use the latest tools and technologies for web development to make client-side solutions.

SPFx (SharePoint Framework) works with React to make client-side web elements for SharePoint. SPFx’s default for building web parts is the React framework, but it also works with Angular and Vue.js, which are other JavaScript options.

The logic of an SPFx web part is written in JavaScript using the React library. When you use SPFx, your code, and its dependencies are built into a single solution that is easy to deploy.

Building SPFx web parts with React is a good idea because the library makes it easy to make UI components that can be used repeatedly and to handle state. React’s excellent performance and SharePoint developers can use the ability to scale to create dynamic user experiences. In addition to other optimizations, the SPFx build process also optimizes the React code. This makes the web component that is made very fast.

In conclusion, SPFx and React are related because SPFx provides a framework for building SharePoint client-side solutions with React, and React it possible to build user interfaces that are responsive, scalable, and fast.

Examples of SPFX React Interview Questions.

Here are some examples of questions that might be asked about SPFx and React development in an interview:

1. Please describe SPFx and how it helps.
2. How well does React work with SPFx when making SharePoint web components?
3. Could you explain a virtual DOM and how it works in React?
4. How do you keep track of states when using React?
5. What is a Higher Order Component, and when might you want to use one in React?
6. What are some best practices for using React to get data from a server in an SPFx web component?
7. How would you make an SPFx web element built in React run faster?
8. How do you handle changes to SharePoint data as they happen in real-time when you use React in an SPFx web element?
9. How much would you use React to make an SPFx web part more responsive?
10. How much have you used React to make SPFx solutions? Can you help me out and show me some of the code?

By asking the candidate the above questions, you can find out how well they know SPFx and React and how well they can use these technologies in the real world.

Conclusion

In conclusion, React is a JavaScript library often used to design graphical user interfaces in SPFx solutions. Many websites and web apps are made with React. During an interview for the job of React developer, it’s essential to show that you fully understand the main ideas behind React. Components, state management, and the virtual document object model are some of the most critical concepts in React. It also helps to know much about SPFx and how it works with React. You may have a good chance of getting a job as a React developer if you are ready for the questions you will be asked during the interview and can show how knowledgeable and skilled you are.