How to Learn React.js

What is React.js? In short, it is a JavaScript library for building user interfaces. It enables a user to create complicated UIs from small pieces of code called components, which work by translating raw data into rich HTML.

React uses a declarative paradigm. It enables a user to learn the language once but write it anywhere, meaning it's highly transportable and versatile. React uses a declarative model that makes code more predictable and simple when it comes to bug fixes.

React is responsible for both the Instagram and Facebook apps. It was originally developed by Jordan Walke at Facebook in 2011 and later rolled out to Instagram. It has since become open source though Facebook still works on its development.

What Is React.js Used for?

React helps build seamless user interfaces (UIs). Rather than updating the browser's actual Document Object Model (DOM) directly for every change, React maintains its own lightweight copy of it, called the virtual DOM. When data changes, React compares the new virtual DOM to the previous version, figures out the smallest set of changes needed, and updates only those parts of the real DOM. This render method results in quick, efficient updates.

React can also use node.js or a React-Native offshoot for use on iOS and Android devices. It can be rendered in the server, browser or on native components. It’s particularly helpful when data changes over time. You can develop within React without having to rewrite existing code. In addition to working well with existing technologies, it also interfaces with various libraries and frameworks.

Unlike many web applications, React doesn’t use templates. Instead, it builds UIs with components. Using components enables abstractions to be built, essentially reducing the complexity of the interface for the user. Components can also make it easier to maintain markup and protect UIs from vulnerabilities.

React makes changes to data really simple. Unlike a traditional JavaScript application, where data needs to be manually changed in the DOM to keep it up to date, React does a process called reconciliation where the system finds changes in data and makes recommendations for how it should look. This rendering is neither a string nor a DOM node.

Most React code is written in JSX, a syntax extension that lets developers write HTML-like markup directly inside JavaScript. It isn't required to use React, but it's the convention nearly all React code follows because it makes component structure easier to read.

Modern React components are also built almost entirely with Hooks — functions like useState and useEffect that let function components manage data and side effects without needing to write class-based components. Hooks became the standard way to write React starting in 2019 and are central to how the library is taught and used today.

Finally, while React itself is a UI library rather than a full application framework, most real-world React projects are built on top of a framework like Next.js, which adds routing, server-side rendering, and other structure React doesn't provide on its own. Anyone learning React today will likely encounter Next.js fairly quickly.

Frequently Asked Questions

This section will answer some commonly asked questions about React. In addition to a foundational understanding of JavaScript, students may want to learn a variety of computer programming languages. To get an overview, read how to pick the right programming language for you to learn.