What is React JS and how does it work? Key features

React.js is a popular JavaScript library for building user interfaces (UI). Originally developed by Facebook, it has revolutionised the way developers create dynamic, high-performance web applications.

In this article we will see what React.js is, how it works and what are the features that make it stand out in the world of web development.

What is React.js?

React.js, commonly known simply as React, is an open source JavaScript library designed to facilitate the creation of user interfaces. It was created by Jordan Walke, a software engineer at Facebook, and first released in 2013.

React focuses on building reusable components, which allows developers to create UI elements that can be used in different parts of the application without having to write the same code multiple times. This ability to reuse components is one of the main advantages of React.

How does React.js work?

Components

In React, everything is built from components. A component is a piece of user interface that can be reused and composed to create more complex interfaces. Components can be as simple as a button or as complex as a complete view of the application.

React components are written in JavaScript and can be defined as classes or functions.

JSX (JavaScript XML)

React uses JSX, a JavaScript syntax extension, which allows you to write code that looks very much like HTML. Although JSX is not required to use React, it is very common because of its ability to make code more readable and easier to write. JSX is transformed into JavaScript calls by a compiler.

Virtual DOM

One of the innovations of React is the use of the Virtual DOM. The DOM (Document Object Model) is an in-memory representation of the HTML document structure. Manipulating the DOM directly can be costly in terms of performance, especially in large web applications with many updates.

React addresses this problem by using a Virtual DOM, which is a lightweight and efficient copy of the real DOM. When the state of a component changes, React updates the Virtual DOM first. It then compares the Virtual DOM with a previous version and calculates the most efficient way to update the real DOM. This process is called ‘reconciliation’ and helps React applications be fast and efficient.

Unidirectional Data Flow

React implements unidirectional data flow, which means that data in a React application flows in only one direction: from parent components to child components. This makes tracking changes in application state more predictable and easier to understand.

State and Props

State and properties (props) are two fundamental concepts in React:

• State: It is a structure that holds information that can change over time. Each component can have its own state. When the state changes, React re-renders the component to reflect those changes.
• Props: This is data that is passed from a parent component to a child component. Props are immutable, which means that a component cannot change them directly.

Key features of React.js

Reusable components

Components in React are highly reusable. You can create modular components and use them in different parts of your application. This not only saves time, but also ensures that your code is more consistent and easier to maintain.

Declarative

React takes a declarative approach to building user interfaces. Instead of describing how something should do something (imperative), you describe what you want to achieve (declarative). This means that developers can describe what the UI should look like in a particular state, and React takes care of managing updates and state changes.

Robust ecosystem

React has a robust and growing ecosystem. In addition to the core library, there are a number of add-on tools and libraries that facilitate application development. Some of the most popular include:

• React Router: To manage navigation and routes in your application.
• Redux: To manage the status of the application more efficiently.
• Next.js: A framework for server-side rendered React applications (SSR).
• Create React App: A tool that allows you to set up a React project quickly without the need to set up a complex development environment.

Active community

React has an active community where there are a lot of resources available, including documentation, tutorials, forums and so on. If you run into a problem, chances are someone has already solved it and shared the solution.

Development with React Native

React is not just limited to web development. Facebook also developed React Native, a library that allows you to build native mobile apps for iOS and Android using the same principles and components as React. Developers can use their React skills to build mobile apps without having to learn a new language from scratch.

Support for TypeScript

React also supports TypeScript, a superset of JavaScript that adds optional static typing. Using TypeScript with React can improve code quality and help prevent bugs before they become problems at runtime.

Development tools

React comes with a set of very useful development tools. The React DevTools, for example, allow you to inspect the component hierarchy of a React application and observe changes in state and props in real time.

Performance Optimizations

React offers several ways to optimize the performance of an application. Some of the most common techniques include:

• Memorization: Using React.memo to avoid unnecessary rendering of components.
• Code Splitting: By splitting the code into smaller chunks that can be loaded on demand, rather than loading the entire application at once.
• Lazy Loading: Loading components only when they are needed.

Upgrades and continuous support

Since its launch, React has received continuous updates that introduce new features and performance improvements. The React team at Facebook and the wider community are constantly working to improve the library and keep it relevant in the ever-changing web development landscape.

React.js has revolutionised user interface development with its component-based approach, robust ecosystem and active community. If you are looking to create dynamic, high-performance web applications, React.js is an excellent choice.

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