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What is React? Examples, Features, Components, Pros and Cons

05th Sep, 2023
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    What is React? Examples, Features, Components, Pros and Cons

    Could you spend your entire day without using your phone or the Internet? Probably, not!  

    We live in an era where mobile phones and web applications have made a significant space in our lives. Everything has gone digital, from shopping to booking cabs, ordering food, and conducting transactions. All of these have been made possible by apps that cater to specific needs. These apps are built upon powerful and reliable frameworks, like React.  

    This guide on 'What is React in software development’ will help you understand the basics of this library, including the following:

    • What is React used for?  
    • What does React do?  
    • What are states in React?  

    Besides, we will answer a few common queries that you may have related to React.js.

    What is React.js? 

    React, and React JS are the same thing. So, if you are looking for - “what is React JS or what is React technology,” here’s the answer!  React is a popular JavaScript library that is widely used for building user interfaces for web applications. Developed by Facebook, React has gained significant popularity in recent years due to its flexibility, ease of use, and efficient performance.  React allows you to build applications using modular and reusable components that can be compared to self-contained building blocks, much like Lego blocks. Each component represents a distinct element of the overall interface and can be combined with other components to create the application's entire user interface.

    But don’t confuse ReactJS or technology with React Query. They might sound similar but differ slightly from each other. So, what is React Query?

    React Query is a preconfigured data management toolkit for ReactJS that gives you straightforward, declarative power and control over server-side state management, data fetching and caching, and error handling without changing the overall state of your application. If you are new to the concept and wish to pursue a course, go through KnowledgeHut's React certification course. By the end of the course, you will start creating different forms of applications.

    React JS History   

    Jordan Walke, a software engineer at Facebook, created ReactJS in 2011. He used the library first on Facebook's newsfeed in 2011 and later on Instagram in 2012.  React was released as an open-source project in May 2013, allowing developers outside of Facebook to use and contribute to the library. Jordan designed React to solve challenges in building complex and dynamic user interfaces. ReactJS introduced the concept of components, self-contained building blocks that can be easily reused and combined to create complex UIs. React also uses a virtual DOM (Document Object Model), a lightweight representation of the actual DOM, to efficiently render changes to the UI. Now that we know what is React application is, let’s find out — what does React do?

    Why React?

    Now that you know — what is ReactJS used for or what is the use of React JS, you will discover why React is important.  

    There are several reasons why React has become a prevalent choice for building user interfaces and what it is used for:

    1. Declarative programming model: React provides a simple and intuitive programming model that allows developers to declare what they want their UI (User Interface) to look like without worrying about how it is implemented.  
    2. Reusable components: React's component-based architecture allows developers to create reusable building blocks that can be easily combined to build complex UIs.  
    3. Virtual DOM: The library uses a virtual representation of the actual DOM, allowing it to efficiently update the UI by only re-rendering the changed parts.
    4. Community support: React has a large and active community of developers who contribute to the project and create complementary tools and libraries.
    5. Cross-platform compatibility: Developers use React to build UIs for various platforms, including web, mobile, and desktop applications.  

    We hope your search for “what is React and why use it” ends here. Let’s find out how we can use this framework.

    How to Use React.js?       

    Unlike other frameworks, such as Angular, React does not impose strict code conventions or file organization guidelines. As a result, developers and teams are free to create their own conventions and implement React in a manner that best suits them.

    React is highly flexible, allowing you to use as much or as little of the library as you need.

    React is a versatile tool that can be used to build small interface elements or complete user interfaces. It can be gradually integrated into existing applications or used to create new applications from scratch. Its adaptability makes it a valuable tool for developers.

    1. Plugging React into a Website 

    To introduce interactivity to an HTML page, one can integrate React into an existing web application via a content delivery network (CDN). This integration enables React to take control of a specific section of the website, including a sidebar, widget, or other reusable and interactive React components with limited React functionality. 

    Plugging React into an existing web application is a straightforward process that requires three simple steps.  

    • Step 1: Add the two primary CDN scripts to the website's HTML index file, which is essential for loading React into the application via a CDN service. 
    • Step 2: Create an <div> in the markup file to indicate where you wish to render and plug the React component. You must also assign a unique ID to this <div>, which you can later refer to in the JavaScript code to identify the location.  
    • Step 3: Create the actual like_widget JavaScript file and run the application. 

    2. Creating a Fully-Fledged React App 

    Although React can be used to create small interface components in existing web applications, it's more practical to leverage its capabilities to build complete web applications. Setting up a React application can be daunting due to its demanding tooling configuration requirements, but there's no need to learn the build setup or configure build tools manually. Facebook's create-react-app is a Node package command-line tool that generates a boilerplate version of a React application. This package provides a consistent structure across React projects, allowing developers to begin working on their React applications immediately.

    React JS Examples

    Undoubtedly, React creates fast, scalable, and efficient applications, due to which it has gained popularity and stability among various developers. Today, big IT giants, among other companies, including startups, are employing React to create web applications.  

    Some of the popular ones are as follows:  

    • Netflix
    • Instagram
    • Facebook
    • Airbnb
    • Uber
    • Reddit
    • WhatsApp Web
    • Khan Academy
    • The New York Times
    • SoundCloud
    • Code academy
    • Discord

    React JS Keys 

    Undoubtedly, The "key" attribute is a unique identifier for each item in the list, allowing React to track and update the specific elements that have changed instead of re-rendering the entire list. When rendering lists of items in React, it's essential to use keys to ensure the optimal performance of your application. Keys should be unique across the list of rendered items but not necessarily globally unique. React only requires keys to be unique among siblings within the same list. Without keys, React may not be able to detect which items have changed, which can lead to unexpected behavior and performance issues. To add a key to a rendered list item in React, you simply need to include a "key" attribute in the JSX element, followed by a unique identifier. For example: 

    { => (
    <li key={}>{}</li>

    In the above instance, "" is the unique key for each list item. React can efficiently update the list when the data changes by including a key without unnecessarily re-rendering the entire list.

    React JS Advantages

    React JS has various advantages for developers creating web applications. Some of them are as follows:

    • React's custom virtual DOM allows for faster performance than traditional DOM manipulation.
    • The framework creates impressive and interactive user interfaces.
    • React is search engine friendly, ensuring easy indexing and discovery of web applications.
    • Its modular architecture and data validation features improve readability and maintainability.
    • The library is compatible with various software architectures.
    • This front-end framework simplifies the web application development process.
    • React improves maintainability and productivity for developers.
    • Its virtual DOM guarantees fast rendering.
    • React can be used to develop mobile apps using the same JavaScript library.
    • ReactJS has a large and supportive community of developers and users. 

    Benefits and Limitations

    While React JS does have various advantages, it also has some limitations. Following are the pros and cons of React JS: 


    • React employs a JavaScript-based virtual DOM, which speeds up web applications compared to traditional DOM manipulation.
    • Because of its versatility, React can be used in a wide range of systems and on both the client and server sides, making it a popular choice among developers.
    • React's component-based architecture and data identification features make large web applications easier to manage by improving clarity and maintainability.


    • React only addresses a portion of the development tools required for building web applications, necessitating the selection of additional techniques for a complete set of development tools.
    • Some programmers may find React's use of inline scripting and JSX unsettling.

    Features of React.js

    Here are some of the key features of ReactJS:

    1. JavaScript Syntax Extension (JSX)  

    For many web developers, JSX is the better option. Although JSX is not essential for React development, a significant difference exists between writing react.js documents in JSX and JavaScript. JSX is a JavaScript syntax extension. We can write HTML structures in the same file as JavaScript code.

    2. Virtual Document Object Model (VDOM)

    ReactJS uses a virtual DOM that updates only the components that need to be updated, making web applications faster and more efficient.

    3. Data Flow and Flux is Unidirectional

    React.js is designed only to support data that flows downstream in one direction. You will require additional features if the data must flow in a different direction. React includes a set of immutable values that are passed to the component renderer as HTML tag properties. The components cannot directly modify any properties, but they do support a call-back function for doing so.

    4. Reusable Components

    React JS uses components that can be reused across different parts of the application. This feature reduces the amount of code required and increases code reusability, making development more efficient.

    5. Debugging

    Because of the extensive community support, testing React apps is simple. Even Facebook provides a small browser extension to help with React debugging.

    If you wish to enhance your knowledge of the front-end framework, pursue KnowledgeHut’s Full-stack Development course.

    Components in React

    Components are the building blocks of a React application that represent a portion of the user interface.

    Here are some of the features of the components:

    • Reusability - Components can be reused in multiple areas of an application, accelerating development time.
    • Nested Components - Components can contain other components within them.
    • Render Method - A component must define a render method to indicate how the component should render in its most basic form.
    • Passing Properties - A component can accept props, properties the parent component passes to specify values.

    Props in React Do? 

    "Props" (short for "properties") are a way to pass data between components. Props are similar to function arguments, and they can be any type of data, including strings, numbers, and even functions.

    When a component receives props, it can render dynamic content based on the data passed in. Props are read-only, meaning a component receiving props cannot modify them. Instead, they can use props to render content or pass them down to child components. To pass props to a component, you can add them as attributes in the component's tag.  For instance, if you had a component called "Button" that you wanted to pass a prop called "label" to, you could use the following code:

    <Button label="Click me!" />
    In the "Button" component, you could then access the "label" prop using the "props" object:
    function Button(props) {
    return <button>{props.label}</button>;

    This would render a button with the label "Click me!". The component could then use the "props" object to access and use any other props that were passed in. 

    State in React

    A "State" is a JavaScript object that represents the current state of a component. It is used to store and manage data that can change over time, such as user input, server responses, or other dynamic data.

    To define a state in a React component, you can use the `useState` hook that was introduced in React 16.8. Here is an example:

    import React, { useState } from 'react';
    function Example() {
    const [count, setCount] = useState(0);
    return (
    <p>You clicked {count} times</p>
    <button onClick={() => setCount(count + 1)}>
    Click me

    In this example, we use the `useState` hook to define a state variable called count and a function called setCount that can be used to update the state. The initial value of the state is set to `θ`.

    When the user clicks the button, the `setCount` function is called to update the `count` state by adding 1 to its current value. This causes the component to re-render, displaying the new `count` value in the `p` element. 

    Using states, React components can respond to user interactions and update their output dynamically, creating dynamic and interactive user interfaces. 

    Props vs State in React.js

    In React, both props and states manage data and control the behavior of components, but they have some fundamental differences. 

    1. Source of Data: Props are passed down from the parent component to its child component, while the state is managed within the component. 
    2. Read-only vs. Mutable: Props are read-only, meaning the child component cannot modify the props it receives. The parent component is responsible for updating the props if necessary. In contrast, the state is mutable, meaning that the component can modify its own state. React will automatically re-render a component when its state changes to the updated state. 
    3. Update Triggers: Props don't update within a component. They are passed down as static values and should be considered immutable. If the parent component changes a prop value, the child component will be re-rendered with the new prop value. In contrast, when a component's state changes, React will instantly re-render the component to reflect the updated state. 
    4. Role in Component: Props pass data and behavior from a parent component to a child component. In other words, props allow for the composition of React components, allowing for the reuse of the same component with different data. States manage the internal data of a component. 

    React JS Prerequisites

    Before starting to learn React, you must have a basic understanding of the following concepts: 

    • JavaScript: React is built with JavaScript and relies heavily on JavaScript syntax and concepts. You should have a good grasp of JavaScript fundamentals like variables, functions, loops, and objects, as well as newer concepts like ES6 syntax and features. 
    • HTML and CSS: React helps build user interfaces, so you should be familiar with HTML and CSS.  
    • Package managers: You should be familiar with package managers like npm and yarn, which are used to install and manage external libraries and dependencies in your project. 
    • Git and version control: Git is a popular version control system that is widely used in the development industry. You should have a basic understanding of how to use Git to manage your code changes and collaborate with other developers. 
    • Command line interface: React development often involves working with the command line interface (CLI) to run build tools, start a local server, or manage project dependencies. You should have some familiarity with using the CLI to navigate the file system and execute commands. 

    Is React Worth Learning?

    React is one of the industry's most popular and widely used front-end web development frameworks. It has a large and active community that provides extensive documentation, tutorials, and support. 

    React's component-based architecture and declarative approach make it an efficient and straightforward tool for building scalable and high-performing web applications. The library also offers a rich ecosystem of tools, libraries, and extensions that simplify web development and enhance the user experience. 

    The Google Trends data illustrates how React's reputation has been slowly growing over time as a result of the inclusion of new functionality. 

    Moreover, React developers earn higher salaries than other technology professionals. The need for React-savvy workers across all geographies is constantly being fueled by the widespread use of React in creating scalable and useful apps., And according to, the average salaries for React developers in the U.S. range from 55k to 110k USD. 

    As per Stack Overflow trends, React is the most popular front-end framework than other front-end frameworks.

    Therefore, if you are interested in web development, particularly in creating dynamic and interactive user interfaces, learning React could be a valuable skill to add to your toolbox. Plus, it will help you earn well.

    Final Takeaway on What is React JS and How It Works?

    This guide on “What is React JS and how it works?” clearly states that React is a powerful and widely-used front-end JavaScript library for building user interfaces. Developed by Facebook, the framework has quickly become a popular choice for building complex and interactive web applications.  

    React's component-based architecture, virtual DOM, and use of declarative programming make it highly efficient, scalable, and easy to maintain. React's large and active community has also created a vast ecosystem of tools, libraries, and resources to support developers in their React projects.  

    Whether you are a beginner or an experienced developer, React is an essential tool to learn for building modern and engaging web applications. KnowledgeHut's Web Development and Designing course and React certification are designed to help developers enhance their skills and bag good-paying jobs.

    Frequently Asked Questions (FAQs)

    1Is React a framework or language?

    React is a library for creating user interfaces, not a framework or a language. React is written in JavaScript, a programming language used to develop web applications, and it is used to create reusable UI components that can be used to build web applications. 

    2Is React JS used on the front end or backend?

    React is usually used on web applications' front end or client side to build user interfaces. It is a library for creating reusable UI components that can be used to build complex and interactive user interfaces in web applications. So, if you were searching for “what is the use of React,” here’s your answer.

    3Is React easy to learn? 

    For people with a solid understanding of JavaScript and fundamental programming concepts, it would be easy to learn React. However, like with any new technology, getting comfortable with the React library and its associated concepts may take some time and practice. 

    4Are React developers in demand? 

    Various companies and organizations are using React to build web applications. Therefore, there is a high demand for React developers with experience in the technology.

    Furthermore, React is often combined with other popular technologies such as Redux, Next.js, and GraphQL, which creates additional opportunities for developers to specialize and become experts in a particular technology stack. 


    Sachin Bhatnagar

    Program Director, FSD

    With 20+ yrs of industry experience in media, entertainment and web tech, Sachin brings expertise in hands-on training and developing forward-thinking, industry-centric curricula. 30k+ students have enrolled in his tech courses.

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