Top ReactJS Interview Questions for Developers in 2025

React continues to dominate the front-end development landscape, so mastering the essential concepts can set you apart in interviews and open up new career opportunities. This guide covers some of the most important and challenging React JS interview questions hiring managers will likely ask in 2025. Whether you’re preparing for your first senior-level role or aiming to solidify your expertise, these React JS interview questions will help you demonstrate your deep understanding of the framework and pave the way for your career advancement.

Basic ReactJS Interview Questions

Master the basics of React components, state, props, and more to build a solid foundation with these basic ReactJS interview questions and answers.

1. What are the features of React?

JSX: JSX is a syntax extension to JavaScript. It is used with React to describe the user interface's appearance. Using JSX, we can write HTML structures in the same file that contains JavaScript code.

Components: Components are the building blocks of any React application, and a single app usually consists of multiple components. It splits the user interface into independent, reusable parts that can be processed separately.

Virtual DOM: React keeps a lightweight representation of the real DOM in memory, known as the virtual DOM. When an object's state changes, the virtual DOM changes only that object in the real DOM rather than updating all the objects.

One-way data-binding: React’s one-way data binding keeps everything modular and fast. A unidirectional data flow means that when designing a React app, you often nest child components within parent components.

High performance: React updates only those components that have changed rather than all the components simultaneously, resulting in faster web applications.

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2. What is JSX?

JSX is a syntax extension of JavaScript. It is used with React to describe the user interface's appearance. Using JSX, we can write HTML structures in the same file that contains JavaScript code.

rendero() {
   return(
      <div>
              <h1 > This is a JSX code</h1>
      </div>
   );
}        

3. Can web browsers read JSX directly?

• Web browsers cannot read JSX directly. They are built only to read regular JS objects, and JSX is not a regular JavaScript object.?
• A web browser can only read a JSX file if transformed into a regular JavaScript object. We use Babel for this.

4. What is the virtual DOM?

DOM stands for Document Object Model. It represents an HTML document with a logical tree structure. Each branch of the tree ends in a node, which contains objects.

React keeps a lightweight representation of the real DOM in memory, known as the virtual DOM. When an object's state changes, the virtual DOM changes only that object in the real DOM rather than updating all the objects. The following are some of the most frequently asked react interview questions.

5. Why use React instead of other frameworks, like Angular?

• Easy creation of dynamic applications: React makes it easier to create dynamic web applications because it requires less coding and more functionality, whereas code tends to get complex very quickly with JavaScript applications.
• Improved performance: React uses virtual DOM, which makes web applications perform faster. Virtual DOM compares its previous state and updates only those components in the real DOM, whose states have changed, rather than updating all the components — like conventional web applications.
• Reusable components: Components are the building blocks of any React application, and a single app usually consists of multiple components. These components have logic and controls and can be reused throughout the application, dramatically reducing development time.
• Unidirectional data flow: React follows a unidirectional data flow. When designing a React app, we often nest child components within parent components. Since the data flows in a single direction, debugging errors and knowing where the problem occurs in an application become easier.
• Dedicated tools for easy debugging: Facebook has released a Chrome extension for debugging React applications. This makes the process of debugging React web applications faster and easier.

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6. What is the difference between the ES6 and ES5 standards?

These are the few instances where ES6 syntax has changed from ES5 syntax:

• Components and Function

// ES5
var MyComponent = React.createClass({
    render: function() {
        return(
             <h 3> Hello World</h3>
        );
    }
});
// ES6
class MyComponent extends React.Component {
      render() {
         return(
             <h3> Hello World</h3>
        );
    }
}        

• exports vs export

• require vs import

// ES5
var React = require('react');
// ES6
import React from 'react';        

7. How do you create a React app?

These are the steps for creating a React app:

• Install NodeJS on the computer. We need NPM to install the React library. Npm is the Node package manager with many JavaScript libraries, including React.

• Install the create-react-app package using the command prompt or terminal.

• Install a text editor you choose, like VS Code or Sublime Text.

8. What is an event in React?

An event is an action a user or system may trigger, such as pressing a key or clicking a mouse.

• React events are named using camelCase rather than lowercase in HTML.
• With JSX, you pass a function as the event handler rather than a string in HTML.

9. How do you create an event in React?

A React event can be created by doing the following:

class Simple extends React.Component {
    work() {
        alert("Good Work!")
    }
    render() {
        return (
               < button onClick= {this.work} > Do some work!</button >
       );
   }
}        

10. What are synthetic events in React?

• Synthetic events combine the response of different browsers' native events into one API, ensuring consistency across browsers.
• The application is consistent regardless of the browser in which it is running. Here, preventDefault is a synthetic event.

function ActionLink() {
      function handleClick(e) {
            e.preventDefault();
            console.log("You just clicked a Link.');
     }
     return ( 
            <a href="#" onClick={handleClick}>
                    Click_Me
            </a>
     );
}        

11. Explain how lists work in React.

• We create lists in React as we do in regular JavaScript. Lists display data in an ordered format.
• The traversal of lists is done using the map() function.

const names = ['Kohli", 'Saif', 'Arun', 'Aamir', 'Arif'];

const listOfNames = () => {
        const listitems = names.map((name) =>
             <li key=(name) >
             (name)
             </li>
        );
        return (
             <ul> (listltems)</ul>
        );
}        

12. Why is there a need to use keys in Lists?

Keys are vital in lists for the following reasons:

• A key is a unique identifier, and it is used to identify which items have changed, been updated or deleted from the lists
• It also helps to determine which components need to be re-rendered instead of re-rendering all the components every time. Therefore, it increases performance, as only the updated components are re-rendered

13. What are forms in React?

React employs forms to enable users to interact with web applications.

• Using forms, users can interact with the application and enter the required information whenever needed. Form contains certain elements, such as text fields, buttons, checkboxes, radio buttons, etc.
• Forms are used for many tasks, such as user authentication, searching, filtering, indexing, etc.

14. How do you create forms in React?

We create forms in React by doing the following:?

class NameForm extends React.Component {
   this.state = {value: "};

   handleChange(event) {
      this.setState({value: event.target.value});
   }
   handleSubmit(event) {
       alert('A name was entered: ' + this.state.value);
       event preventDefault():
   }
   
   render() {
     return (
         < form onSubmit={this.handleSubmit.bind (this)}>
            <label>
            Name:
            <input type="text" value=(this.state.value}
onChange={this.handleChange.bind(this)} />
           </label>
           <input type="submit" value="Submit" />
        </form>
      );
   }
}        

The above code will yield an input field with the label Name and a submit button. It will also alert the user when the submit button is pressed.

15. How do you write comments in React?

There are two ways in which we can write comments:

• Single-line comments

In [8]:     |  #Returns sum of two values
              |  def sum(a, b):
              |        return a + b
              |
              |  x = sum(4, 7)
              |  print(x)
              |
              | --------------------------------
                11        

• Multi-line comments

Return (
    {/*
       Multi
       line
       comment
    */}
    < div>
          <p>Hello</p>
    </div>
);        

16. What is an arrow function and how is it used in React?

• An arrow function is a short way of writing a function to React.
• It is unnecessary to bind ‘this’ inside the constructor when using an arrow function. This prevents bugs caused by the use of ‘this’ in React callbacks.

without arrow function

render(){
     return(
           <Myinput onChange={this.handleChange.bind(this) } />
     );
}        

with arrow function

render(){
      return(
            <Mylnput onChange={(e) => this.handleOnChange(e)} />
      );
}