What is ReactJs? [Beginners Guide]

If you are a Web developer or an aspiring Web developer then you must know what is ReactJS, why you need to learn ReactJS, and what you can do with it. By the end of this tutorial, you will have a good understanding of what is ReactJS, the features of React, the benefits of using React, whether you should learn React or not, and how to create your first React project.

So let's get started.

What is ReactJS?

• ReactJS is one of the most popular front-end JavaScript libraries, known as React.

• It is used for creating modern component-based user interfaces for web applications.

• ReactJS is an open-source library maintained by Facebook (now Meta) and a group of independent developers and businesses.

• The current version of the ReactJS library is React 18, and soon React 19 is about to launch. You can find the official documentation of ReactJS on react.dev website.

• ReactJS is used for creating SPAs or Single Page applications.

• ReactJS enables you to create user interfaces as a collection or group of individual components. A component is not like an HTML tag, instead, it is a functional unit, with UI elements, and functional parts, both combined together.

• As per StackOverflow Developer Survey 2023, when it comes to web frameworks and technologies, 40.58% of developers around the world use ReactJS.

• Because of the massive adoption of ReactJS, the community of developers using ReactJS is huge right now, and therefore you will find a lot of small packages and libraries useful for building modern web applications. Yes, readymade components, that you can just plug in and use.

Time for an Example. In ReactJS, if you want to create a card with an Image, Title, and Like button, then you can create 3 components,

• Image component

• Title component

• LikeButton component

• All these 3 components are combined to create a Card component. So every individual component is a reusable unit.

As you can see in the example above, using ReactJS you can build reusable UI components. The Image, Title, and Like components were used together inside the Card component, similarly, these can be used in some other components too.

History of ReactJS

• ReactJS was created by Jordan Walke, a Facebook Software Developer, who was tasked to find a solution to improve the performance and maintainability of the user interface at Facebook.

• The initial version of ReactJS was called FaxJS. It was created in 2011 and presented in an internal Hackathon at Facebook. Later it was launched to the world in 2013 at JSConf US.

• The main idea behind creating a library like ReactJS was to have a JS library that can be used to develop large data-driven web applications, that are easy to manage and can perform well on different devices like Desktop, and Mobile.

• Soon after its launch in 2013, ReactJS became very popular very fast, because developers around the world wanted a solution to build fast, responsive, dynamic web applications for different devices.

Features of ReactJS

Here are some of the top features of ReactJS.

1. JSX or JavaScript XML

JSX allows you to use an HTML-like syntax to create UI in your React application. The JSX code is compiled into JavaScript code before the application is run in the browser.

const element = <h1>Hello, Studytonight!</h1>;

2. Component-based Architecture

Components are the building blocks of a React application. Components are pure JavaScript functions that return UI elements. In a React component, you can have the logic as JavaScript code, and create a user interface using JSX.

React components can be created as JavaScript functions that return JSX code which is rendered as the user interface. You can create multiple components, and then combine different components together to create complex user interfaces, just like in the image above.

function STApp(props) {
  return <h1>Welcome, {props.name}</h1>;
}

const element = <STApp name="Abhishek" />;

3. Virtual DOM

The use of a virtual Document Object Model, or virtual DOM, is another noteworthy feature of ReactJS. React builds an in-memory data structure to represent the actual DOM (this is called virtual DOM). Any change in the UI is first done in the virtual DOM, and then the actual DOM is updated.

ReactJS calculates how efficiently and with minimum changes the actual DOM can be updated as per the virtual DOM.

4. Javascript Expressions

When you use JSX to code the user interface, you can directly include the JS code using {} curly brackets.

For example, you can iterate over an array using the map() function and List down all the array elements in the user interface. Or have conditional rendering in the UI using the ternary operator directly in JSX code.

5. State

ReactJS supports state management using which you can control updates to the user interface without accessing the UI elements in the DOM. Yes, you have to modify the state data, and React automatically updates the User interface by re-rendering the components.

React has a useState hook, a useReducer hook for state management, and the context API too for managing state

6. Props

Props stand for properties. It is used to pass on data from parent components to child components. Props are function parameters, so you can pass on data as an argument when you call functions.

7. Hooks

Hooks are predefined JavaScript functions that perform a certain operation in the ReactJS ecosystem.

• The useState hook is used to create a state variable.

• The useEffect hook is used to control effects in a React component.

Similarly, there are many other hooks available in React. You can also create your own custom hooks if you want.

8. Module System

ReactJS uses the modern ES module system so that you can structure your code properly into directories and different files, and use the import and export statements to use them.

Create your first React Project

If you want to create a React project, then you need NodeJS installed on your local machine. With NodeJS installation npm and npx will be automatically installed. Using npx, you can run the create-react-app command to create your ReactJS project.

npx create-react-app DIRECTORY_PATH

You can specify the path of the directory in which you want to set up the ReactJS project.

You can also create a directory with some name (for example, first-react-app), open your terminal or command line tool, go to the directory using the cd command, and run npx create-react-app . command to set up the React project in the current directory.

After successful setup, this is the structure of the project that you will get:

You can run the project by executing the command: npm run start and you will get the following web app in the browser.

For a detailed step-by-step guide, and to understand each step followed to create a ReactJS project in detail, check out our How to Create ReactJS Project guide.

Advantages of ReactJS

• ReactJS makes use of a virtual DOM that uses an in-memory data structure cache, with only the most recent updates being modified in the browser's DOM. This improves the app's efficiency.

• Using the react component element, you can build components of your choosing. The modules are reusable and useful for code maintenance.

• Easy to learn

• Huge Ecosystem and large community

• Since much of the code is performed in Javascript rather than HTML, it's simple to debug and evaluate.

• Performance

• SEO-friendly

• Easy to understand Data flow

• Easy to Host

• Package management is easy with npm

Frameworks of ReactJS

There are many frameworks built on top of ReactJS. With time, ReactJS has become a core library around which many frameworks have been built. Here are some of the popular ones that you can explore:

1. NextJS

2. Remix

3. Gatsby

You can learn more about them from React's documentation here.

ReactJS Prerequisite

If you want to learn ReactJS, then before getting started with ReactJS, you must first learn a few other things, and they are:

1. HTML - because JSX is based on HTML

2. CSS for styling webpages

3. JavaScript, especially ES6 and later features.

Knowledge of JavaScript is super important before you start learning ReactJS. ReactJS is a JavaScript library, which is entirely based on JavaScript and all the modern JS features are used in ReactJS. So you better master JavaScript first and then learn ReactJS.

Should I learn React in 2024?

Yes, definitely. If you want to become a Web developer, then you should learn JavaScript, then learn ReactJS.

There are many frameworks based on ReactJS. You can also learn NextJS because the ReactJS team is also promoting NextJS. NextJS is completely based on ReactJS at its core with a lot of new features added on top of it.

FAQs

Here are some of the frequently asked questions about ReactJS.

Q. What is ReactJS used for?

ReactJS or React is used for developing modern component-based user interfaces. It is especially suited for creating complex data-driven user interfaces. The UI created using ReactJS is super fast, responsive, and performs well on different devices like desktop and mobile devices.

Q. ReactJS is a Framework?

ReactJS is not a framework. ReactJS or React is a JavaScript library.

Q. Can I make the backend using ReactJS?

No. ReactJS is used for developing the frontend of a web application. You can interact with the backend services using ReactJS, and use the data that you get from the backend in the UI. But you cannot create the backend using React.