React Introduction

1. What is React?

React, also known as React.js or ReactJS, is a powerful JavaScript library widely used for building user interfaces, particularly single-page applications. Developed by Facebook in 2013, React has revolutionized the way developers create web applications. Its core philosophy revolves around the concept of reusable components, enabling developers to build complex UIs from small, isolated pieces of code.

One of the standout features of React is its virtual DOM (Document Object Model). Unlike traditional approaches that manipulate the browser’s DOM directly, React creates a virtual DOM in memory. This approach results in highly efficient updates and rendering of web pages, offering a smooth and responsive user experience.

2. How Does React Work?

React’s working mechanism is centered on its component-based architecture and the virtual DOM. Let’s break it down:

  • Component-Based Architecture: In React, everything is a component. A component is essentially a JavaScript function or class that returns a piece of JSX (JavaScript XML). JSX looks like HTML and is used to describe the UI. Components can have their own state and lifecycle methods, allowing them to manage data and behavior independently.
  • Virtual DOM: When a component’s state changes, React first updates the virtual DOM. Then, it compares the updated virtual DOM with the previous version, calculates the best possible method to make these changes in the browser’s DOM, and performs the necessary updates. This process, known as ‘diffing,’ ensures that the real DOM is updated in the most efficient way possible.


class Welcome extends React.Component {
  render() {
    return <h1>Hello, {}</h1>;

This simple class component Welcome takes a property name and renders a greeting message.

3. React.js History

React was first developed at Facebook in 2011 for the company’s newsfeed feature. By 2013, it was open-sourced, allowing developers worldwide to contribute to its growth and evolution. The library quickly gained popularity due to its unique approach to building user interfaces, particularly its virtual DOM feature, which addressed performance issues that traditional data binding methods faced.

Over the years, React has undergone numerous updates, each enhancing its capabilities and performance. Notable milestones include the introduction of Hooks in version 16.8, which allowed for state and other React features in functional components, and the concurrent mode in later versions, further optimizing the rendering process for complex applications.