In the world of web development, one of the most popular and widely used technologies is React, also known as React.js or ReactJS. Front-end development has grown exponentially over the years with React at the core of the revolutionization of how developers build dynamic user interfaces.

In this section, you will learn what React is, why it is a popular choice for programmers and why you should use it for your web development projects.

In order to follow the lessons in this course, you need to have a good understanding of HTML, CSS and most importantly JavaScript.

What is React?

React is an open-source library developed and maintained by Facebook, now Meta. It is widely used for building user interfaces and allows developers to create web applications with interactive and dynamic user experience.

React is specifically designed for creating Single Page Applications commonly known as SPAs. SPAs are simply applications where users interact with the user interface (UI) without triggering page reloads. The dynamism and intuitive nature of React gave it its name - as it ‘reacts’ quickly to changes and adjusts the UI accordingly without causing a reload.

Before React came into the scene, applications were rendered on the server-side which makes applications reload after each user interaction. This made applications slower and cumbersome for users especially with large applications.

Server-Side Rendering (SSR) is a process where the server generates a fully rendered HTML page for each user request and sends it to the browser. The browser displays the static HTML first. JavaScript is then downloaded and executed to make the page interactive.

But with React, applications are rendered on the client-side and gives an almost ‘instantaneous’ feel on interaction, which greatly improves user experience with large applications.

Client-Side Rendering (CSR) is a process where the server sends a minimal HTML file with links to JavaScript and CSS, and the browser handles rendering the content dynamically. The browser downloads and executes the JavaScript framework or library (e.g., React) to construct the DOM and display the content.