• Articles
  • Tutorials
  • Interview Questions

What is React.js? The JavaScript Library

What is React.js? The JavaScript Library

React.js is quickly becoming the go-to choice for web development in India today, drawing in developers from across the nation. Its immense popularity stems from its ability to deliver exceptional user experiences.  In this blog, we will be going through the key features of React.js, how one can set up a React development environment, and different other components of React.

Table of Contents:

Watch our React JS video tutorial for practical tips to learn React:

What is React.js?

React.js, often referred to as React, is an open-source JavaScript library designed for building user interfaces with simplicity and efficiency in mind. It functions as the front-end view layer in the Model View Controller (MVC) architecture, which focuses exclusively on the visual aspect. With React, developers can craft modular user interfaces, encouraging the creation of reusable components for displaying dynamic data.

In React, a component-based architecture is followed, where UI elements are divided into reusable components. These components encapsulate the logic and structure of a particular part of the UI, thereby making it easier to develop and maintain complex applications. React provides a declarative approach to building UIs, thus allowing developers to describe how the UI should look based on the current application state. It efficiently updates and renders the UI when changes occur, resulting in a more responsive and interactive user experience.

Ready to build amazing user interfaces? Join our React course today!

Why Use React.js?

React.js can prove beneficial to users around the world. Some of the reasons why one should use React are mentioned below:

  • Virtual DOM and Performance Optimization: React.js utilizes a virtual DOM (Document Object Model) to efficiently update and render the UI. React minimizes the direct manipulation of the browser’s DOM by creating a virtual representation of the actual DOM, thus resulting in significant performance improvements. This approach allows for faster rendering and efficient updates, making React ideal for building complex and interactive applications.
  • Component-Based Architecture: React follows a component-based architecture, promoting modular development and code reusability. Components encapsulate their logic and rendering, thus allowing developers to create reusable UI elements. This modularity enhances code organization, readability, and maintainability, thereby enabling efficient teamwork and easier debugging.
  • Declarative Syntax: React’s declarative syntax simplifies UI development. Developers can focus on describing the desired outcome rather than manipulating the DOM directly. This makes code more predictable and easier to understand, thus reducing the likelihood of errors and quickening the development time.
  • React Native for Cross-Platform Development: React Native, which is built on top of React, extends its capabilities to mobile app development. With React Native, developers can build native mobile apps for both iOS and Android platforms using JavaScript. This eliminates the need for separate codebases and allows for efficient code sharing, thus saving time and effort in cross-platform development.

Check out this blog on React JS Error Boundaries!

Key Features of React.js

Key Features of React.js

Mentioned below are some of the key features of React.js:

  • Performance Optimization: React.js employs techniques like ‘memoization’ and ‘shouldComponentUpdate’ to optimize performance by limiting unnecessary re-renders while efficiently updating the components as necessary.
  • Accessibility: React.js facilitates the development of accessible web applications by supporting ARIA (Accessibility Rich Internet Application) attributes and helping developers craft inclusive user experiences.
  • Community Support: The vibrant community associated with React.js offers regular updates, documentation, tutorials, and resources that enable developers to stay current while troubleshooting issues quickly and efficiently.
  • Unidirectional Data Flow: React.js ensures a uniform data flow from parent to child components for predictable updates and easier debugging. This further facilitates predictable updates and easier debugging by maintaining this one-way flow of information from parent to child components.
  • Rich Ecosystem: React.js is home to an expansive ecosystem of libraries, tools, and community support, thus providing developers with ample resources while making integration easier with other technologies.

Get your React JS basics clear through our React JS Tutorial.

Setting Up the Development Environment

Setting Up the Development Environment

To begin developing with React.js, you need to set up your development environment. Mentioned below is a step-by-step guide to the same:

  • Installing Node.js: Node.js is required to run React applications. Visit the official Node.js website and download the latest stable version for your operating system. Follow the installation instructions provided by the installer.
  • Creating a New React Project: Once Node.js is installed, you can use the Node Package Manager (npm) to create a new React project. Open your terminal or command prompt and navigate to the desired directory where you want to create the project. Run the below-mentioned command to create a new React project under the name “my-react-app”:
    npx create-react-app my-react-app
    The command mentioned above creates a new folder with the project structure and installs all the necessary dependencies.
  • Running the React Application: For running the React application, navigate to the project directory using the following command in your terminal:
    cd my-react-app
    Now run the following command to start the React application:
    npm start
    This launches the development server and opens the application in your default web browser. Now, you can successfully view and interact with the default React application.
  • Exploring the Project Structure: The React project structure consists of various folders and files. Of them, the most important files are mentioned below:
    • src: This folder contains the source code of your React application.
    • src/index.js: This file/folder is the entry point of the application, where the ReactDOM renders the root component.
    • src/App.js: This file/folder is the default component representing the main application.
    • src/App.css: This file/folder is the default CSS file for styling the App component.
    • public/index.html: This is the HTML template file that serves as the entry point for the application.

The files and folders mentioned above provide a solid foundation for starting your React development journey.

Get 100% Hike!

Master Most in Demand Skills Now !

Go through these Android Interview Questions to excel in your interview.

What is JSX in React.js?

React.js uses JavaScript XML (JSX), enabling developers to write HTML-like code using JavaScript while seamlessly blending UI and logic.

const element = <h1>Hello World!</h1>

As seen above, JSX differs significantly from both HTML and JavaScript; it uses its own format for content development.

JSX is an extension of JavaScript with full compatibility with ECMAScript 2015’s syntax (ES6).

JSX tags can contain names, attributes, and children elements. When enclosed within curly braces, the value of an attribute becomes an expression in JavaScript.

What are State and Props in React.js?

React.js provides powerful tools to manage data through its State and Props architecture. With this architecture, React components can seamlessly exchange data, thanks to props. These props enable components to share information, boosting their reusability and flexibility. It’s like giving different parts of your website the ability to talk to each other, making your code more efficient and adaptable.

An example of state and props:

import React, { useState } from 'react';
// Child Component
const ChildComponent = (props) => {
return (
<p>Value from Parent (via props): {props.valueFromParent}</p>
// Parent Component
const ParentComponent = () => {
// State example
const [parentState, setParentState] = useState('Hello from Parent!');
// Props example
return (
<ChildComponent valueFromParent={parentState} />
const App = () => {
return (
<h1>React State and Props Example</h1>
<ParentComponent />
export default App;

Here, we have used state and props. Let’s see what’s happening in this code:

  • It consists of two components: `ParentComponent` and `ChildComponent`. 
  • In `ParentComponent`, there’s a state (`parentState`) using the `useState` hook, initialized with the message “Hello from Parent!”. This state is displayed in an `<h1>` tag. 
  • The `ParentComponent` also renders the `ChildComponent`, passing `parentState` as a prop to it. In `ChildComponent`, the received prop is displayed in a paragraph tag. 

In simple terms, the parent holds a message in its state, and the child displays that message using props. This illustrates the fundamental concepts of state and props in React, enabling communication between parent and child components.

What are Components in React.js?

Components in React.js are the essential building blocks of user interfaces. These reusable, self-contained units comprise the logic and presentation for those parts of an online application that are considered parts. The two categories of React components are mentioned below: 

  • functional components 
  • class components

Functional components can be defined using simple JavaScript functions that take props (properties) as input and return JSX (JavaScript XML) output that defines their structure and content.

Class components are like special classes written in the ES6 version of Javascript built on the React. Class components bring in additional capabilities like lifecycle methods and state management. Essentially, they offer developers a way to create components using a class-based approach.

Components enable developers to modularize their code, promote reusability, and build a structured and maintainable codebase. Their declarative approach simplifies the building of UIs, thus making React.js easier for newer developers.

How to Create Components in a Module?

Take a look at the code mentioned below for creating components in React.js. This code demonstrates the usage of functional and class components in React and shows how one can render child components within a parent component:

import React from 'react';
// Functional Component
const FunctionalComponent = () => {
  return <h1>Hello, I'm a functional component!</h1>;
// Class Component
class ClassComponent extends React.Component {
  render() {
    return <h1>Hello, I'm a class component!</h1>;
// Parent Component
class ParentComponent extends React.Component {
  render() {
    return (
        <h1>Parent Component</h1>
        <FunctionalComponent /> {/* Rendering a functional component */}
        <ClassComponent /> {/* Rendering a class component */}
export default ParentComponent;

In the example above, we have created three components: FunctionalComponent, ClassComponent, and ParentComponent.

The above-mentioned code is written in JavaScript, utilizing the React library. It defines three components: FunctionalComponent, ClassComponent, and ParentComponent.

FunctionalComponent showcases an easier means of creating components in React. Being stateless, it returns a JSX code; in this case, an element displaying “Hello, I’m a functional component!” is returned.

ClassComponent showcases an older way of creating React components. Being a stateless component, it returns JSX as well. Here, an element with text reading “Hello, I’m a functional component!” is created using ClassComponent.

The ParentComponent from above showcases another class component that renders an <div> element with a <h1> heading “Parent Component.” Inside the <div>, it renders an instance of the components, FunctionalComponent and ClassComponent, used as child components.

Prepare for your next React JS interview by going through our React Interview Questions.

Future of React.js

The future of React.js seems bright. Some of its features that will advance in the near future are mentioned below:

  • Strong Community and Ecosystem: React.js boasts a vibrant and active community, which contributes to its continuous growth and improvement. Its vast ecosystem offers numerous libraries, tools, and frameworks that enhance React development. Community support ensures that React will continue to evolve, thereby introducing new features and improvements over time.
  • React Fiber and Concurrent Mode: React Fiber, an ongoing internal reimplementation of the core algorithm of React, aims to improve performance and enable better handling of complex UI scenarios. Concurrent Mode, a new feature introduced in React, allows for better handling of asynchronous operations and provides smoother user experiences. These advancements showcase React’s commitment to staying at the forefront of web development.
  • Adoption by Major Companies: React.js has gained widespread adoption from industry giants such as Facebook, Instagram, Airbnb, and Netflix. This adoption by major companies not only validates the capabilities of React but also ensures its continued growth and support. The involvement of these companies further fuels React’s innovation and establishes it as a reliable choice for large-scale applications.
  • React as a Skill for Developers: With its growing popularity and demand in the job market, learning React.js equips developers with a valuable skill set. Its relevance and extensive usage across various industries make React.js a safe investment for professional growth and career prospects.


In a rapidly evolving tech landscape, investing time and effort into learning React.js is a wise decision that can open doors to exciting opportunities and empower you to build innovative web experiences. By mastering the ins and outs of React.js, developers can enhance their productivity, build dynamic UIs, and create interactive web applications.

Get answers to all your React queries through Intellipaat’s Web Community.

Course Schedule

Name Date Details
Web Development Courses 01 Jun 2024(Sat-Sun) Weekend Batch
View Details
Web Development Courses 08 Jun 2024(Sat-Sun) Weekend Batch
View Details
Web Development Courses 15 Jun 2024(Sat-Sun) Weekend Batch
View Details