Top 50+ React Interview Question & Answers

As of today, there are around 1,000 contributors on GitHub. Isn’t that impressive? One of the reasons React stands out is its unique features, like the Virtual DOM and reusable components, which grab the attention of front-end developers everywhere. Even though React is just a library for ‘View’ in the MVC (Model-View-Controller) model, it's still giving tough competition to full-blown frameworks like Angular, Meteor, and Vue. Curious to see how React compares to other JS frameworks? Check out the graph below to see the trend of the most popular JavaScript frameworks!

Scope of React

Choosing the right technology for your web or application development can be tricky, right? But React has emerged as one of the fastest-growing JavaScript frameworks today. It's no surprise that the demand for React certification is growing rapidly. Developers love React because it offers a quick learning curve, clean abstraction, and reusable components. It's a favorite for front-end development. And the best part? React keeps evolving, so there’s no stopping it anytime soon. So, are you ready to dive into React and boost your development skills?

React Interview Questions for Beginners

React Interview Questions for 3 Years of Experience

React Interview Questions for 5 Years of Experience

React Interview Questions for 10 Years of Experience

React Interview Questions and Answers for Beginners

1. Describe What is React.

Facebook created the front-end JavaScript library React in 2011. React uses a component-based methodology that allows you to create reusable user interface components. It’s primarily used for building dynamic and complex mobile and web user interfaces.

2. What characteristics does React have?

React's key characteristics include:

• It supports Server-side rendering.
• It uses Virtual DOM instead of the real DOM to optimize performance.
• It follows a unidirectional data flow (data binding).
• It enables the construction of UI using reusable or composable components.

3. What are the most important benefits of utilizing React?

Several key benefits of React include:

• Learning React is easy and intuitive.
• It adheres to the MVC design pattern.
• React improves efficiency with Virtual DOM.
• It allows you to easily create dynamic web applications.
• It’s great for SEO optimization.
• It supports reusable components.
• Comes with practical tools.
• Has a large and active community.
• React supports a variety of code-testing methods.

4. What are the main drawbacks of React?

Here are the key drawbacks of React:

• React is just a library, not a full-fledged framework.
• Its extensive library can take time to fully understand.
• Beginner developers might find it challenging to grasp and write React code.
• It uses JSX and inline templating, which may be confusing for some and complicates coding.

5. Describe JSX.

JSX stands for JavaScript XML. It is an extension of JavaScript that allows you to write HTML-like syntax within your JavaScript code. JSX enhances React’s functionality by allowing developers to create UI components that are easier to understand and maintain. Preprocessors, like Babel, convert JSX expressions into standard JavaScript code.

6. Why is JSX unreadable by browsers?

Browsers can only read JavaScript objects, but JSX is not a standard JavaScript object. To make JSX understandable to browsers, we must use JSX transformers (like Babel) to convert it into JavaScript code, which browsers can then execute.

7. Why is JSX used by us?

• Performance: JSX allows for faster execution as it gets converted to JavaScript.
• React uses components that combine both markup and logic, which simplifies code structure.
• It offers type-safety and lets most problems be caught during compilation.
• JSX simplifies the creation of templates within React applications.

8. What does Virtual DOM mean to you?

The Virtual DOM is essentially a lightweight copy of the actual DOM. It is used by React to improve performance. React’s render function builds a virtual DOM tree representing the elements, attributes, and content as JavaScript objects. When there is a change in the data model, React updates this virtual tree and then applies necessary changes to the real DOM efficiently.

9. Describe how Virtual DOM operates.

The Virtual DOM operates in three stages:

1. When any data in the React application changes, the Virtual DOM representation of the user interface is re-rendered.
2. It then compares the new Virtual DOM with the previous one, finding the differences.
3. Only the modified items are updated in the real DOM, resulting in efficient rendering.

10. What does React's render() method achieve?

Every React component must have a render() method. This method returns the HTML that should be displayed by the component. It's important to note that all elements to be rendered must be wrapped in a single parent element like a <div> or <form>.

Read More - React Roadmap

11. How may multiple components be integrated into one?

There are various methods in React that allow you to integrate multiple components into one, helping build complex user interfaces. These methods include:

• JSX Composition: Combining multiple components using JSX.
• Passing Components as Props: You can pass components as props to child components to combine them into one.
• Conditional Rendering: Dynamically render components based on certain conditions.
• Higher-Order Components (HOCs): These are functions that take a component and return a new component with additional functionality.
• Render Props: A technique for sharing code between React components using a function prop.

12. What Do React Props Mean?

Props (short for properties) are an essential feature in React. They allow data to flow from parent components to child components. Similar to HTML attributes, props store values passed to a component. They are immutable, meaning you cannot modify props within a component. You can think of props as arguments to a function, allowing you to pass data between components in a reusable way.

13. In React, what is a State?

State is a fundamental concept in React that allows components to create dynamic, interactive user interfaces. Unlike props, which are immutable, the state can be updated within a component to reflect changes. States are objects that manage the data of a component, and they control how the component is rendered. You can access and modify the state using this.state().

For more information on React states, check out this guide.

14. Distinguish in React between States and Props.

Here are the key differences between State and Props in React:

15. In React, how can the State of a component be updated?

To update the state of a component in React, you use the this.setState() method. This method ensures that the component re-renders with the updated state. It's important to note that state updates are asynchronous, so the state might not be immediately updated after calling setState().

Example:

import React, { Component } from 'react';
class Counter extends Component {
 constructor(props) {
 super(props);
 this.state = {
 count: 0,
 };
 }
 incrementCount = () => {
 this.setState({ count: this.state.count + 1 });
 };
 render() {
 return (
 <div>
 <h1>Counter</h1>
 <p>Count: {this.state.count}</p>
 <button onClick={this.incrementCount}>Increment</button>
 </div>
 );
 }
}
export default Counter;    

React Interview Questions and Answers for Intermediate

16. Define the differences between React's stateless and stateful components.

17. What is the purpose of an arrow function in React?

Arrow functions are essentially a condensed form of function expression writing syntax. The functions are also referred to as "fat arrows" (=>). Due to ES6's default lack of auto-binding, these functions enable the components' contexts in React to be bound correctly. Most of the time, arrow functions come in handy when interacting with higher-level functions.

18. What does React define as an event?

Events in React are the responses that are set off by particular actions, such as key presses, mouse clicks, and mouse hovers. Managing these events is comparable to managing DOM element events. However, there are some syntactical variations, such as the following:

1. Events are named in camel case rather than only lowercase.
2. Functions are passed in place of strings when passing events.

19. How may an event be created in React?

You may create a React event by carrying out the following example:

import React, { Component } from 'react';
class MyComponent extends Component {
 // Event handler function
 handleClick = () => {
 alert('Button clicked!');
 }
 render() {
 return (
 <div>
 <h1>React Event Example</h1>
 <button onClick={this.handleClick}>Click me</button>
 </div>
 );
 }
}
export default MyComponent;    

20. What do React's synthetic events mean?

• The objects that serve as a cross-browser wrapper for the native event of the browser are known as synthetic events.
• They create a single API that combines several browsers' behaviors.
• This is done to ensure that the properties displayed by the events are consistent across various browsers.

21. How do controlled and uncontrolled components in React vary from one another?

22. Describe Lists in React.

• Data can be shown in an ordered way using lists. Lists in React can be formed similarly to how they are in JavaScript.
• With the help of the map() method, we may go through the list's elements.

23. What use do keys provide in React?

• The UI is driven by data that corresponds to distinct Virtual DOM Elements, which are identified by keys.
• By reusing every element already present in the DOM, they assist React in rendering as efficiently as possible.
• These keys have to be distinct strings or numbers, or else React simply rearranges the elements rather than re-rendering them.
• The performance of the application increases as a result.

24. How are React forms created?

• HTML forms and React forms are comparable.
• However, with React, the state is updated exclusively through setState() and is stored in the component's state property.
• As a result, a JavaScript function manages the elements' submissions and prevents them from immediately updating their state.
• The information that a user enters into a form is fully accessible to this function.

25. What stages does the lifecycle of a React component go through?

The life cycle of a React component has the following phases:

1. Initial Phase
2. Mounting Phase
3. Updating Phase
4. Unmounting Phase

26. Define the lifecycle methods of React components.

The important React lifecycle methods are:

• getInitialState()
• componentWillMount()
• componentDidMount()
• componentWillReceiveProps()
• shouldComponentUpdate()
• componentWillUpdate()
• componentDidUpdate()
• componentWillUnmount()

27. What do React's Pure Components mean?

The simplest and fastest components that can be written are called pure components. Any component with merely a render() can be swapped out. These elements improve the application's functionality and code simplicity.

28. What are React's Higher Order Components (HOC)?

• React's higher-order components are a sophisticated React method for reusing component logic.
• This function accepts a component as input and outputs a new one. Stated otherwise, this function takes another function as an input.
• The official website states that it is a pattern that results from React's compositional structure rather than a feature or part of the React API.

29. How does React's HOC work?

HOC can be used for a wide range of tasks, some of which are listed below:

• Code Reusability
• Props manipulation
• State manipulation
• Render hijacking

30. What distinguishes a React component from an element?

Elements and components in React differ mostly in the following ways:

React Interview Questions for Experienced

31. What is the React commenting process?

We can write comments in React just like we would in JavaScript. Two possible methods are:

1. Comments in a single line
2. Multiple-line comments

32. Why does React need component names to begin with a capital letter?

The component names in React must begin with a capital letter. The component name will throw an error as an unrecognized tag if we start it in lowercase. The reason behind this is that JSX treats tag names in lowercase HTML tags.

33. In React, what are fragments?

React components that return multiple elements employ fragments. It lets you group a list of several offspring without expanding the DOM with another node.

34. Why do fragments work better in React than container divs?

• Because fragments do not generate additional DOM nodes, they operate more quickly and use less memory.
• Maintaining the intended layout might be challenging with certain CSS styling, such as CSS Grid and Flexbox, which introduce <div> tags in the middle and have unique parent-child relationships.
• There is less clutter in the DOM Inspector.

35. How can I use React validation on props?

• props validation is a tool that aids developers in preventing faults and issues in the future.
• It improves the readability of your code.
• PropTypes is a unique property used by React components that helps you find errors by verifying the data types of values supplied through props.
• You do not have to define components with propTypes in order to use them.
• We may use App.propTypes in the React component to apply validation on props.
• The JavaScript console will display warnings if any properties are supplied with an invalid type.
• You must set the App.defaultProps after defining the validation rules.

36. Describe create-react-app.

Facebook announced the Create React App tool to help developers create React applications. You can use it to construct React apps that are one page in length. You can avoid time-consuming setup and configuration tasks like Webpack or Babel by using the preset create-react app.

37. In React, how do you make a component?

In React, there are two ways to construct a component:

• Function Components: The easiest method for creating a component in React is this one. These are the only JavaScript functions that return React elements and take an object called props as their first parameter.
• Class Components: You can define a component using the ES6 class, and the class components function makes it easier.

38. What exactly are React hooks?

React state and lifecycle aspects can be "hooked into" from a functional component using hooks, which are functions. Class components are not compatible with React Hooks. They permitted us to compose parts without a class. Common hooks include useState, useEffect, and useContext.

Read More: Most Asked React Hooks Interview Questions in 2025

39. Which guidelines should you adhere to when using React's hooks?

When using Hooks in your code, you have to abide by two rules:

1. React Hooks can only be invoked at the highest level. Calling them from within loops, conditions, or nested functions is prohibited.
2. Calling the Hooks is only permitted from React Function Components.

40. How do forms work in React?

• Forms are used by React to facilitate user interaction with web applications.
• Users can interact with the program and enter the necessary data whenever needed by using forms.
• Certain elements are present in forms, including radio buttons, checkboxes, buttons, and text fields.
• Numerous functions, including user identification, searching, filtering, indexing, and more, are accomplished by using forms.

41. How do you interpret the term "props" in React?

Props are inputs to components in React. They have naming conventions similar to HTML tag attributes and can be single values or objects holding a set of values supplied to components upon creation. They are information that a parent component transmits to a child component. The following component functionality is the primary function of props in React:

• Give your component access to custom data.
• The status of the trigger changes.
• Use via this.props.reactProp within component's render() method.

42. How do refs work in React?

• The abbreviation for References in React is Refs.
• This attribute serves to keep a reference to a specific React element or component that the render configuration function of the component will return.
• It is employed to provide pointers to specific elements or components that render() has returned.
• They are useful when we need to add methods to the components or when we need to measure the DOM.

43. What are React's Forward Refs, and when are they used?

• One feature that is utilized to send a reference from one component to one of its child components is called ref forwarding.
• The React.forwardRef() function can be used to carry it out.
• It works very well with higher-order components and is utilized specifically in libraries of reusable components.

44. In React, which is the better choice—callback references or findDOMNode()?

• Callback references are a better solution than the findDOMNode() API.
• Because findDOMNode() precludes some future enhancements in React, and callback refs provide better control when the refs are set and unset.

45. What is React Router and how does React require it?

• Developed on top of React, React Router is a robust routing library that facilitates the addition of new screens and processes to the application.
• By doing this, the URL and the data that is shown on the webpage are kept up to date.
• It is used to create single-page web apps and has a consistent structure and behavior.
• It's easy to use React Router's API.

46. Describe React Router's benefits.

The following list includes React Router's key benefits:

• It is not required to manually set the browser history in this case.
• Link is used to navigate the application's internal links. It is comparable to the anchor element.
• For rendering, the Switch function is used.
• There is only one Child element required by the router.
• All of the components are listed in <Route> in this.
• The three packages that make up the packages are Web, Native, and Core. It supports the React application's small size.

47. What distinguishes Conventional Routing from React Routing?

React routing and conventional routing differ in the following ways:

48. Describe the concept of flux.

The unidirectional data flow is enforced by the architectural pattern known as flux. Utilizing a central store with authority over all data, it facilitates communication between various components and manages generated data. Any updates to the data across the application must happen exclusively here. Flux lowers run-time errors and gives the program stability.

49. Explain Redux.

One of the most popular front-end development libraries available today is Redux. It is utilized for the overall state management of JavaScript applications and provides a predictable state container. Redux-developed applications are simple to test and exhibit consistent behavior across many settings.

- Read Here: Most Asked Redux Related Interview Question and Answer

50. What three key principles does Redux adhere to?

• One and only source of truth: An object/state tree inside a single store contains the state of the entire application. It is simpler to debug or inspect the program and to keep track of changes over time using a single state tree.
• Read-only status: An action must be triggered in order to alter the state. A simple JS object that describes the change is called an action. The action is the minimal representation of a change to the data, the same as the state is the minimal representation of data.
• Modifications are made using pure functions: Pure functions are required to define the actions' transformation of the state tree. Functions classified as pure have a return value that is exclusively determined by the values of their inputs.

51. What is the difference between useEffect and componentDidMount?

52. How can you optimize performance in a React application?

• Using React's PureComponent or React.memo to avoid unnecessary re-renders.
• Implementing lazy loading with React.lazy and Suspense for code splitting.
• Using the useCallback and useMemo hooks to memoize functions and values.
• Avoiding inline functions and objects as props.
• Minimizing the use of the global state and keeping components as stateless as possible.

53. Explain the Context API in React.

• It provides a way to share values between components without passing props manually at every level.
• It is used to manage the global state in a React application.
• The createContext function creates a context, and Provider and Consumer components are used to pass and consume the context value, respectively.

54. What is React Suspense?

• React Suspense is a feature that allows components to wait for something like data fetching before rendering.
• It provides a way to declare a loading state while the component waits for asynchronous operations to complete.
• It works well with React.lazy for lazy loading components.

55. How does the useReducer hook work?

• The useReducer hook is used for managing complex state logic in React.
• It accepts a reducer function and an initial state and returns the current state and a dispatch function.
• It is similar to Redux but is built into React.
• The reducer function specifies how the state should change in response to actions dispatched by the component.

56. How do you handle forms in React?

• Forms in React can be handled using controlled or uncontrolled components.
• In controlled components, form data is handled by the component's state, typically using the useState hook.
• In uncontrolled components, data is handled by the DOM itself, usually with refs to access form values.

57. What are React Portals and how do you use them?

• React Portals provide a way to render children into a DOM node that exists outside the hierarchy of the parent component.
• They are used for rendering elements like modals, tooltips, or dropdowns that need to visually break out of the parent container.
• You can create a portal using ReactDOM.createPortal(child, containerNode).

58. How do you handle errors in React components?

• Errors in React components can be handled using error boundaries.
• An error boundary is a component that catches JavaScript errors in its child component tree, logs those errors, and displays a fallback UI.
• It is created using a class component with the componentDidCatch lifecycle method and a getDerivedStateFromError static method.

59. What is React.memo and when would you use it?

• React.memo is a higher-order component that prevents a functional component from re-rendering if its props haven't changed.
• It is used for performance optimization by memoizing the component and is useful when you have a component that renders the same output given the same props.

60. Explain the difference between useRef and createRef.

• useRef is a hook that returns a mutable ref object whose .current property is initialized to the passed argument.
• It persists between renders and can be used to store a reference to a DOM element or any mutable value. createRef is a method used in class components to create a ref.
• It returns a new ref object that can be attached to a DOM element via the ref attribute.
• useRef is typically used in functional components, while createRef is used in class components.

Summary

In this article, we’ve walked you through React interview questions for every skill level, from beginner to advanced. We’ll start with the basics like JSX, Virtual DOM, and components, then move to more complex topics like lifecycle methods, hooks, and routing. Each section comes with questions and answers to help you build the knowledge and confidence you need to excel in your React interview.

Looking to dive deeper? Check out our ReactJS Certification Training to enhance your skills and boost your career. Plus, if you're just starting out, you can access our free ReactJS course, or explore our free Angular course. It’s the perfect way to learn at your own pace!

Test Your Knowledge of React!

Q 1: What is React?

• (a) A JavaScript library for building user interfaces
• (b) A JavaScript framework for building web applications
• (c) A server-side language
• (d) A database management system

Q 2: What is the virtual DOM in React?

• (a) A real-time DOM representation in memory
• (b) A JavaScript object representation of the DOM
• (c) A database for storing UI elements
• (d) A storage solution for React components

Q 3: What is JSX in React?

• (a) A syntax extension for JavaScript that allows HTML-like code
• (b) A CSS preprocessor
• (c) A JavaScript testing library
• (d) A React-specific event-handling system

Q 4: What are props in React?

• (a) Properties passed to components
• (b) A way to manage state
• (c) Methods for handling events
• (d) A component lifecycle method

Q 5: What is the difference between state and props in React?

• (a) Props are mutable, and state is immutable
• (b) State is used to manage data within components, while props are used to pass data between components
• (c) Props are used for local component data, and state is used for global data
• (d) There is no difference between state and props

Q 6: What is the purpose of the `componentDidMount` method in React?

• (a) To initialize state
• (b) To fetch data after the component mounts
• (c) To update the DOM
• (d) To handle user events