What are the Features of React.js?

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 such as:

1. Component-based Architecture

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.

2. Virtual DOM

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.

Advantages of the Virtual DOM

• It minimizes direct updates to the real DOM, reducing expensive operations and speeding up rendering.
• Changes are first made in the Virtual DOM and then selectively updated in the real DOM, optimizing the process.
• Enables rendering on various platforms, like web and mobile, with the same codebase.
• Smooth updates without reloading the entire page, providing a faster, more responsive UI.
• It offers a clear structure for tracking changes, which simplifies debugging.

3. JSX (JavaScript XML)

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.

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.

4. Unidirectional Data Flow or One-way Data Binding

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.

Advantages of Unidirectional Data Flows

Here are the advantages of unidirectional data flow:

• Data flows in a single direction (parent to child), making tracing issues and understanding the application's behaviour easier.
• Clear data flow simplifies tracking issues
• Simplified State Management  to control data

Disadvantages of Multiple data flows

Here are the disadvantages of multiple data flow:

• Increases difficulty in managing data flow, especially in large apps.
• Harder to trace data-related problems.
• Risk of unsynchronized data across components.
• Makes the app harder to maintain due to complex data management.

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

5. Reusable Components

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.

6. React Ecosystem

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). 

7. Community and Resources

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.

8. Server-Side Rendering (SSR)

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.

9. Mobile Development (React Native)

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.

Portability For Mobile Applications

• Build iOS and Android apps using a single codebase.
• Reuse most of the code across both mobile and web platforms.
• Significantly reduces time by allowing code sharing between platforms.

React Native Advantages 

Here are the advantages of react native in mobile development:

• Instantly view changes in the app without restarting.
• Native components enhance performance, close to native apps.
• Large ecosystem of libraries and tools.
• Access to device-specific features (camera, GPS, etc.) via native code.

10. Developer Tools

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.

11. Immutability

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.

12. Context API

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.

13. Hooks

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.

1. useState

useState is a React hook that lets you add state variables to functional components.

2. useEffect

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.

3. useContext

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

14. Conditional Statements and Conditional Rendering

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!

16. Extension (New Feature)

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:

1. Functional Components

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

• This is a functional component in React, named Greeting.
• It takes props as an argument, which is an object containing values passed to the component.
• props.name is accessed and displayed inside an <h1> tag, dynamically rendering the value of the name prop.

2. Class Components

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:

1. Install Node.js along with npm

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.

2. Install Create React App

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.

3. Create a New React Application

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.

4. Change Directory into Your Project

Once the application is created, navigate to the project folder:

cd my-react-app

// 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;

This will take you into the directory where your React app is located, and you can start working on it.

5. Edit the Application

The edit function in react.js allows you to modify or update components, state, or event handlers in the code.

 // 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.

6. Run the Development Server

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.

7. Start Coding Your React Application

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.

8. Build for Production

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

• The App component is a prop called isPass. If it is true, the App will display "Success! You Passed!". If it is false, it will display "Sorry, You Failed!".
• The isPass value is passed from the index.js file while the application is rendered.
• The ReactDOM.render() method will render the App component inside the root element of the HTML page.

Why Do We Use React.js?

We use react.js for the following reasons:

1. Cross-platform

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.

2. SEO-friendly

React supports server-side rendering by sending pre-rendered HTML to the browser, thus improving SEO performance.

3. Scalable

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.

4. Modular

The component-based architecture encourages modularity, which speedens up development, brings organization to the system, and provides ease of maintenance.

5. Flexible

React is built to be highly flexible, integrating with innumerable libraries and other tools; it supports web and mobile application development.

6. Performance

With the Virtual DOM, React minimizes DOM manipulation, ensuring fast rendering and improved performance.

7. Reusability

React enables you reuse the components and, reduces the maintenance burden by duplicating fewer codes.

8. Better Accessibility

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:

Here are some advantages using react.js such as:

• Encourages reusability and maintainability by allowing UI to be built with reusable components.
• Predictable code that's easier to debug by describing UI and its state.
• With many libraries and tools (such as Redux and React Router), time taken for developing increases.
• Developers provides active support and a lot of resource materials.
• Server-side rendering support enables improved indexing on search engines.
• Build once and share code between Web and Mobile apps, provides an edge on productivity.

Here are the disadvantages of using react.js such as:

• Must know concepts like JSX, hooks, and state management.
• Might add unnecessary complexity to simple applications.
• React apps may face challenges with SEO as they heavily depend on JavaScript without SSR.
• Large ecosystem may create confusion while picking up libraries or some tool.
• Developing process and fast pace of React may lead to frequent refactoring or upgrades.

Here are the examples of real time web applications uses react such as:

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.

1. Is React.js frontend or backend?

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.

2. Why is React a preferred choice for programming?

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.

3. What is React mostly used for?

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.

4. What is the main function of React?

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