Reactjs: An Introduction to the Popular JavaScript Library

Reactjs is a popular JavaScript library used for building user interfaces. Developed by Facebook, it has gained widespread popularity among developers due to its simplicity and efficiency. This article will explore the basics of Reactjs, its key features, and how it works.


Getting Started with Reactjs

To get started with Reactjs, you must understand HTML, CSS, and JavaScript. Once you grasp these fundamentals, you can create a new Reactjs project using a package manager like npm or Yarn.
The basic structure of a Reactjs application consists of components, which are the building blocks of a user interface. Each component represents a part of the UI and can contain other components or HTML elements. Components can also be passed data via props, similar to function arguments.

Components and Props

In Reactjs, components can be created using either functions or classes. A functional component is a simple function that returns a JSX element, while a class component is a JavaScript class that extends the React. Component class.

Props are used to pass data between components. They are similar to function arguments in JavaScript. Props can be used to pass data from a parent component to a child component, and they can also be used to pass data between sibling components.

State and Lifecycle

The state is used to manage the data in a Reactjs component. Unlike props, a state can be changed by the component itself. State changes can trigger a re-render of the component and its children.

Reactjs also provides a set of lifecycle methods that allow developers to control the behaviour of a component during its lifetime. For example, the componentDidMount() method is called after a component is rendered for the first time, while the componentWillUnmount() method is called just before a component is removed from the DOM.


JSX is a syntax extension for JavaScript that allows developers to write HTML-like code in their JavaScript files. JSX is used to create elements in Reactjs. JSX elements are converted into JavaScript objects by the Reactjs compiler, which is then rendered to the DOM.

Reactjs Hooks

Reactjs Hooks are a set of functions that allow developers to use state and other Reactjs features in functional components. The useState() hook is used to manage the state in a functional component, while the useEffect() hook is used to perform side effects in a functional component.

Handling Forms in Reactjs

Reactjs provides a way to handle forms using controlled components. A controlled component is a component that manages its state and updates the state when the user interacts with the form. Uncontrolled components are another option for handling forms in Reactjs.

Reactjs Router

React Router is a popular library used for routing in Reactjs applications. It provides a way to create routes in a Reactjs application and to pass data between routes. React Router also provides a set of lifecycle methods for managing the behaviour of a component during its lifetime.


Redux is a state management library that can be used with Reactjs. It provides a centralized store for managing the application state and can connect components to the store using the connect() function.

What is React used for?

React provides a way to create reusable UI components that can be used to build complex web applications with dynamic and interactive user interfaces. React allows developers to easily manage an application’s state, providing a simple and efficient way to handle events and data flow between components.

React can build many applications, from simple web pages to single-page applications. It is commonly used for building web and mobile applications and creating interactive dashboards and data visualization tools.

Some famous examples of applications built using React include Facebook, Instagram, Airbnb, Netflix, and Uber. React is also widely used in developing open-source projects and in creating design systems and component libraries.


Reactjs is a popular JavaScript library used for building user interfaces. It provides a simple and efficient way to create components, manage state, and handle events. Reactjs is constantly evolving, and new features are added regularly. As a result, it has become a popular choice among developers for building modern web applications.

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