Published: 26 Feb 2025 | Reading Time: 5 min read
React.js, commonly referred to as React, is a widely-used open-source JavaScript library that was developed and maintained by Facebook. It plays a crucial role in crafting user interfaces, particularly for single-page applications where the content updates dynamically in response to user interactions. By enabling developers to construct fast, responsive, and engaging user experiences through reusable components, React has emerged as one of the top choices in web development. In this blog, we will delve into the features of React.js and how it functions in application development. We will also provide illustrative examples.
React.js is a declarative, efficient, and flexible JavaScript library for building user interfaces. The library is developed and maintained by Facebook. Unlike traditional web development methods where HTML is manipulated, React enables you to specify what the UI should look like at any time while ensuring that the UI is updated as quickly as possible when the application state changes. Moreover, it uses a virtual DOM for faster updates.
Jordan Walke, a software engineer at Facebook, developed React.js in 2011 to address the issues of operating complex UIs and frequent state updates in large-scale applications. First used within Facebook's News Feed and Instagram, it soon became apparent that React's approach to building dynamic user interfaces had enormous potential. In 2013, React was open-sourced at JSConf US, marking the beginning of its ride to popularity within the web development community.
In 2014, React introduced JSX, allowing the use of HTML-like elements in JavaScript code for easier UI visualization and angular updates. The release of React 16 in 2017 saw the introduction of Fiber architecture, which greatly enhanced performance and flexibility, introducing features such as error boundaries and portals, which improve UI handling.
By 2018, React introduced Hooks allowing the utilization of state and lifecycle features in functional components, making the code less cumbersome and easy to read. React's component-based architecture and use of a virtual DOM made it popular and consolidated its position amongst some of the most influential front-end libraries of modern web development.
Here are the react.js features to build web applications:
React allows developers to split the User Interface into independent components. These components are the basic building blocks of React, and each is a standalone unit of code that can be reused across an application, making the management of complicated UIs more easy. The components may have the state and logic inherent in them.
VDOM is nothing more than an in-memory representation of the actual DOM. React uses the VDOM (Document Object Model) to change the actual DOM only on parts that have changed. The Virtual DOM is like a copy of the real DOM. When something changes in the web app, the Virtual DOM is updated and compared to the real one. If there are any differences, only the changed parts are updated in the real DOM, keeping everything else the same. This makes React really fast.
JSX is a JavaScript Syntax Extension or JavaScript XML. It is a syntax that allows the combination of HTML and JavaScript in coding. It allows developers to easily use HTML within JavaScript. This process helps convert HTML tags into elements in React, simplifying the visualization of the basic structure of the user interface where the logic is implemented. While React allows UI code to be written without JSX, utilizing JSX can enhance code readability and foster better organization and maintainability.
Example:
const name="Nxtwave";
const ele = <h1>Hello Learners! to {name}</h1>;
Code Explanation: The code defines a constant name with the value "Nxtwave" and creates a JSX element ele, which displays "Hello Learners! to Nxtwave" when rendered in React.
React works on a unidirectional data flow from parent components to child components in a React application through props. This makes data flow predictable and easier to debug.
Example:
function Parent() {
const message = "Hello from Parent!";
return <Child message={message} />;
}
function Child(props) {
return <h1>{props.message}</h1>;
}
Explanation: The message is passed from the Parent to the Child component as a prop, ensuring the data only flows in one direction (top-down).
Output: Displays "Hello from Parent!" in an <h1> element
React encourages the building of reusable components. This modular way allows a component to be written once and reused all over the app, thus reducing code duplication and ensuring easy maintenance.
The React ecosystem comes with a whole lot of other libraries and tools that complement the functionality of it. Some of the well-known libraries fall in line with React Router (handling routing), Redux (handling state), and Next.js (handling server-side rendering).
By virtue of the users' involvement, React is a web technology of developers that continues to thrive through a process of improvement and support. Such resources include tutorials, documentation, and open-source libraries provided to help developers.
Server-side rendering allows the React component to be rendered on the server and provides an HTML response that can be sent to the browser. Thus, it reduces the initial load time and helps with SEO, making it easier for search engines to crawl pre-rendered sites.
React Native permits developers to build mobile applications using React and Javascript, aimed at both iOS and Android platforms. It allows developers to reuse code across both web and mobile platforms, thereby saving time and effort in development.
React has very powerful developer tools, one of which is the React Developer Tools browser extension, to inspect the component tree, view the component state and props, and allow for debugging of applications.
React encourages immutability, meaning you should not change the data directly. You create a new copy of the data with the updated value that makes it much easier to track state changes and debug it.
The Context API is a way of sharing data across all the components in the component tree without passing props through every level. It is useful for situations in which you'd want to implement global states, like user authentication or themes.
React Hooks is a way for function components to manage state and effects of version 16.8. The most common called primitive Hooks: They enable cleaner and more readable code. The most commonly used primitive hooks are useState, useEffect, and useContext.
useState is a React hook that lets you add state variables to functional components.
useEffect is a hook that enables you to perform side effects in functional components, such as fetching data, subscribing to events, or manually changing the DOM.
useContext is a hook that lets you access the value of a context directly in a functional component. It helps share values (like authentication state, theme, etc.) across components without prop drilling.
Code Example:
import React, { useState, useEffect, useContext } from 'react';
// Create a Context for the user
const UserContext = React.createContext();
const UserProfile = () => {
// Using useState to manage local state
const [user, setUser] = useState({ name: 'Deepthi', age: 30 });
// Using useEffect to update document title when the user changes
useEffect(() => {
document.title = `User: ${user.name}`;
}, [user]); // Dependency array ensures the effect runs when `user` changes
// Using useContext to access shared context data
const contextValue = useContext(UserContext);
return (
<div>
<h1>{contextValue.greeting}, {user.name}!</h1>
<p>Age: {user.age}</p>
<button onClick={() => setUser({ name: 'Varun', age: 25 })}>
Change User
</button>
</div>
);
};
const App = () => {
return (
<UserContext.Provider value={{ greeting: 'Hello' }}>
<UserProfile />
</UserContext.Provider>
);
};
export default App;
Explanation: The above code enables managing state, side effects, and the context in function components. useState handles local state, useEffect manages side effects like updating the document title, and useContext provides access to shared data.
Output:
Initially, the page will show:
Hello, Deepthi!
Age: 30
After clicking the "Change User" button, the state changes, and the page will update to:
Hello, Varun!
Age: 25
In react, conditional rendering allows you to display content based on conditions. You can use JavaScript operators like if, ternary operator, or && to conditionally render UI elements based on the application's state or props. Conditional statements are used for conditional rendering. The computer executes statements in the order of control flow in the script. This helps determine which blocks of a program should be represented.
Example:
function Greeting(props) {
return (
<div>
{props.isPass ? <h1>Success! You passed!</h1> : <h1>Sorry, you failed!</h1>}
</div>
);
}
Explanation: If isPass is true, it will show a success message; otherwise, it will show a failure message.
Output:
//When isPass is true:
<Greeting isPass={true} />
//output
Success! You passed!
This is one of the new react.js features used with conditional rendering and one-way data binding together. For instance, you could have some message change in the parent component based on user input and then have that conditionally rendered in the child component.
React.js is a component-based architecture, wherein applications are built by combining smaller, reusable units known as components.
The core components of React.js are:
Basic JavaScript functions returning JSX for rendering UI. They accept props and return UI elements.
Example:
function Greeting(props) {
return <h1>Hello, {props.name}!</h1>;
}
Output:
<Greeting name="Deepthi" /> //Input taken from user
Hello, Deepthi! // ouput on the screen
Explanation:
<h1> tag, dynamically rendering the value of the name prop.ES6 classes that extend React.Component. These contain the lifecycle methods and can manage state directly.
class Greeting extends React.Component {
render() {
return <h1>Hello, {this.props.name}!</h1>;
}
}
Explanation: The code defines a Greeting class component that extends React.Component. It has a render() method that returns JSX, displaying the value of the name prop inside an <h1> tag. The component dynamically renders "Hello, {name}" where name is passed as a prop, such as "Hello, Deepthi!" if name="Deepthi".
Output:
<Greeting name="Deepthi" /> //Input
Hello, Deepthi! // output on the screen
Here are the steps you need to follow to create a react application:
First of all, to manage the packages and run your React app, you will need Node.js and npm(Node Package Manager). Download and install Node.js from nodejs.org.
After the installation of Node.js and npm, on your terminal or command prompt type the following command to install create-react-app tool globally:
npm install -g create-react-app
This will make it easy to start a new React project with all the required configurations.
Now that you have installed the tool, you can start a new React application with a single command:
npx create-react-app my-react-app
Change my-react-app to the name you want to give your project. This will create a folder containing all the basic codes with necessary files required to help you get started with React.
Once the application is created, navigate to the project folder:
cd my-react-app
This will take you into the directory where your React app is located, and you can start working on it.
The edit function in react.js allows you to modify or update components, state, or event handlers in the code.
// App.js
import React from 'react';
function App(props) {
return (
<div>
{props.isPass ? <h1>Success! You passed!</h1> : <h1>Sorry, You failed!</h1>}
</div>
);
}
export default App;
// index.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
ReactDOM.render(<App isPass={true} />, document.getElementById('root'));
Alternatively, you can change isPass={false} to see the difference in the output.
With the project set up, you can now start the development server by running:
npm start
This will launch your app in the browser on http://localhost:3000, and the development server will check for any changes you make to the code and update the app automatically.
This is the exciting part! Open the project folder in your code editor. The src folder contains your main files for your react components including App.js and index.js. Now you can start editing these files, add new components, and style your application.
When you're done with your application and want to prepare it for deployment, you can build the optimized production version by using: npm run build
Output:
1. When isPass={true} in index.js:
Success! You passed! //Output displayed on browser
2. When isPass={false} in index.js:
Sorry, You failed! //Output displayed on browser
Explanation:
We use react.js for the following reasons:
It allows the common usage of React components for creating mobile applications on iOS and Android platforms, thereby reducing the development cost as time is saved.
React supports server-side rendering by sending pre-rendered HTML to the browser, thus improving SEO performance.
The component-based architecture in React allows the application to scale up effortlessly with growing needs. The large apps can be broken down into smaller components, which can be handled easily.
The component-based architecture encourages modularity, which speedens up development, brings organization to the system, and provides ease of maintenance.
React is built to be highly flexible, integrating with innumerable libraries and other tools; it supports web and mobile application development.
With the Virtual DOM, React minimizes DOM manipulation, ensuring fast rendering and improved performance.
React enables you reuse the components and, reduces the maintenance burden by duplicating fewer codes.
React provides a significant advantage in the development of accessible applications, rendering support for ARIA (Accessible Rich Internet Applications) attributes and tools like react-aria.
Here are the differences for Node.js and React.js:
| Node.js | React.js |
|---|---|
| Powers the backend that is involved with server tasks and loads of backend processing. | Powers the frontend and engages with the creation of interactive, dynamic user interfaces with instant responses. |
| Handles server-side logic, requests, and real-time communications seamlessly | Builds responsive, interactive UIs and provides a seamless user experience. |
| Uses an event-driven, non-blocking I/O model for multitasking execution | Uses reusable components to create scalable, easily manageable UIs. |
| Quickly performs database management, authentication, and backend services. | UI rendering is the focus, ensuring instant updates and engaging interactions with the user. |
| It has MVC architecture which helps better structuring of the backend logic | Does not follow an MVC approach; modular components are used for smoother UI development. |
| Interaction with the DOM is zero; the applications are totally developed on server-side, and then the required JSON is sent to the client. | Manages the Virtual DOM that becomes the front end for fast, efficient UI updates, eliminating needless re-rendering. |
| Runs on a Chrome V8 engine and improves performance for backend tasks. | Occurs in a browser and provides a smooth user experience. |
| Controls backend services, APIs, and real-time data flow with smooth performance. | Renders alive UIs, creating more engaging user experiences with smooth state management. |
| Runtime optimizes the execution of JavaScript code through the V8 engine for back-end performance. | Utilizes VDOM to optimize the rendering on the front end and render the parts that are updated only. |
Here are some advantages using react.js:
Here are the disadvantages of using react.js:
Here are the examples of real time web applications uses react:
1. Facebook: Developed by Facebook and majorly used in its platform for dynamic news feeds, user interactions, and more, this framework lays the basis for many of Facebook's features wherein they are based on user interactivity.
2. Instagram: This is also owned by Facebook, implements React for its web application. React is responsible for the feed, general user interactions, and creating and managing reactjs dynamic form builder content, ensuring super fast updates and a seamless experience when images are uploaded or users comment or like posts.
3. Netflix: The interface of Netflix is also driven by React. It leverages the capabilities of React to allow for smooth transitions, the dynamic loading of content, and an overall excellent experience when users are searching through movies or TV shows. The interface also is capable of managing content recommendations based on individual preferences.
4. Airbnb: Airbnb's website also uses React to ensure smooth user experience in areas like searching for listings, booking accommodations, and managing user data. It load more functionality in react js quickly and instantly to users' interactions.
5. Dropbox: Dropbox uses React in its web application to organize files and folders with ease and efficiency. It allows users to easily upload, share, and organize files, providing an intriguing and reactive experience.
6. WhatsApp Web: It uses React to handle real-time messaging, media sharing, and notifications. Its efficiency ensures that messages are updated instantly, without reloading the page, hence fast-paced engagement on the web.
7. Uber: Uber uses React for both its driver and rider applications. React provides a complete interactive and smooth experience to its users by enabling real-time rendering of the map interface, ride requests, and driver statuses.
8. Trello: It is a project management application that uses React to manage its dynamic boards, lists, and cards. React guarantees speedy updates on boards without having to refresh the entire web view.
In conclusion, the features of react.js allow developers to create modern web applications more efficiently and effectively. Its component-based architecture alongside the virtual DOM, declarative syntax, and ecosystems enable developers to engineer dynamic, maintainable, and high-performance user interface solutions. The mobile development supported by React Native, server-side rendering improving SEO, and the Context API assisting in state management, React has become a very powerful tool for developers in the web development.
ReactJS is a frontend JavaScript library used for building user interfaces. It focuses on the view layer in an application, mainly managing the appearance and behavior of the UI in web applications.
The component-based architecture of React, which allows UI elements to be reused, is responsible for making it popular. It offers some performance improvements due to the virtual DOM, provides a vast ecosystem, and boasts a declarative syntax that's easier for development.
React is most commonly referred to as building interactive dynamic user interfaces for web applications. It is a reliable option for building single-page applications in which the UI loads updates without reloading the entire page.
The main function of React is to facilitate the creation and manipulation of UI components that respond to changing data accordingly (state/props). It only re-renders UI components when changes on the virtual DOM.
React.js Roadmap for 2025: Beginner to Advanced - Follow the best React.js roadmap to master essential skills, from beginner basics to advanced concepts, and become a skilled React developer (Published: 02 Jan 2026, 6 min read)
Axios in React.js: Steps & API Calls - Axios in React JS is a promise-based HTTP client used to make API requests for data fetching, submission, and handling responses or errors in React applications (Published: 02 Jan 2026, 6 min read)