What is React? A complete explanation of the leading web development library

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React has revolutionized web development Over the last decade, it has become one of the most powerful and popular tools for creating dynamic, fast, and maintainable user interfaces. If you're wondering what exactly React is, what it's used for, and why it's been chosen by everyone from giants like Facebook and Netflix to emerging startups, you've come to the right place. In this article, we thoroughly unravel all the aspects you need to know, from its origins to its inner workings, including its advantages, functionality, ecosystem, use cases, and differences with React Native.

In today's web development industry, knowing React is almost essential.. More and more companies and developers are betting on this library Thanks to its flexibility, performance, active community, and ease of learning for those already proficient in JavaScript. Here you'll find a complete and easy-to-understand guide, written in Spanish, so you can understand the ins and outs of React in a clear and natural way.

What is React and what is it used for?

React is a open-source JavaScript library Initially developed by Facebook (now Meta) and a broad community, it aims to create interactive user interfaces for web and mobile applications. Its main objective is facilitate and optimize the construction of modern application views through reusable components and efficient management of state and interface logic.

React is often confused with a framework, but it's actually more focused on the view layer. This means that It is only responsible for creating and updating the graphical interface of the application, leaving the developer free to choose additional libraries for routing, advanced state management or requests to servers, such as Redux or React Router.

React was first introduced publicly in 2013, although its development began earlier as an internal solution at Facebook to improve the performance and maintainability of its news feed and Instagram views. Since then, the library has grown tremendously in popularity and functionality, becoming an essential tool for front-end web development.

History and evolution of React

The birth of React occurred in 2011, when Facebook engineer Jordan Walke designed a prototype called “FaxJS” Inspired by XHP concepts for PHP. The need was clear: improve Facebook feed performance in the face of the interface synchronization and update issues caused by existing solutions at the time. After several internal tests and its adoption on Instagram, React was finally released as open source at JSConf US in 2013.

In its early years, React quickly established itself as a leading library, in part due to the large community of developers who began contributing and developing it. Companies like Netflix, Airbnb, and Dropbox embraced React for their platforms, giving it even more momentum and visibility.

Throughout its evolution, React has introduced key improvements such as the virtual DOM, declarative programming, functional and class components, and the famous Hooks (introduced in version 16.8 in 2019), which revolutionized the way state and lifecycle are managed in functional components.

Another key milestone was the launch of React native In 2015, allowing the creation of native mobile apps for iOS and Android using the same logic and syntax as React. In 2017, Facebook modified the project's license to MIT, responding to community demands and removing restrictions that had generated controversy.

Main features of React

• Component Based: Every React application is made up of independent, reusable pieces called componentsThese can be functional or class-based and encapsulate logic, structure, and style, allowing you to separate and reuse pieces of the interface in different parts of the project.
• Virtual DOMReact uses an in-memory representation of the real DOM. When it detects changes to data or state, it updates only the necessary parts after comparing the new virtual DOM tree with the old one. This allows for huge performance improvements and a smoother user experience..
• JSX SyntaxJSX is a syntactical extension of JavaScript that makes it easy to write HTML-like structures directly within JavaScript code, combining logic and presentation. It provides flexibility and readability, and simplifies the insertion of JS variables and expressions into component markup.
• declarative programmingComponents describe what the interface should look like for each possible state, and React takes care of automatically updating them when data changes.
• One-way data flow: Data is transmitted from upper components to lower components by means of props, making it easier to track and debug changes.
• State Management: Each component can maintain its own state, which represents a specific "snapshot" in time. State can be shared or managed globally using tools like Redux or Recoil in larger projects.
• Component life cycle: React offers methods and hooks that allow you to execute logic at different stages of a component's life: creation, updates, and deletion.
• Extensible and open ecosystemFrom the beginning, React has embraced open source and an active community that maintains and evolves a massive ecosystem of plugins, tools, extensions, and learning resources.

How React works internally

At the core of React is the virtual DOMWhen a state change occurs in a component (for example, after a button click), React doesn't directly update the browser's DOM, which would be a costly and slow process. Instead, it generates a virtual version of the DOM in memory, compares the new tree with the old one (a process known as diffing) and applies only the necessary changes to the actual DOM.

This process minimizes costly DOM manipulations and significantly improves performance, especially in applications with many updates and interactive components. The result is fast and efficient rendering., a feature that has made React famous.

Another key point is the use of JSXAlthough not required, most developers prefer JSX because it makes code more understandable and compact, allowing variables, functions, and JS logic to be inserted directly into the component’s HTML, and also protects against XSS attacks by converting expressions to secure strings before rendering.

The typical flow in React is: the developer creates one or more components, defines their state and props, and describes in JSX how the interface should look for each case. When the user interacts (e.g., submitting a form), React updates the corresponding state, resulting in a quick and efficient update of the affected part of the UI.

Types of components in React and their differences

In React there are functional and class componentsClass components have long been the standard, but since the introduction of hooks, functional components have become the recommended and most widely used option.

• Functional components: These are JS functions that return a fragment of JSX. Thanks to hooks (such as useState o useEffect), can now manage state, side effects, and other advanced capabilities previously only available in class components. For a deeper dive into how to manage data loading and performance, you can check out
  

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• Class components: These are ES6 classes that extend React.Component and must implement, at least, the method render(). Manage state using this.state and the life cycle by methods such as componentDidMount, componentDidUpdate y componentWillUnmount.

Nowadays, the trend is to write most of the logic with functional components and hooks, since the code is simpler, easier to test and understand.

Props, State, and the Lifecycle in React

props Properties are how components receive data or functions from their parent components. They are immutable within the child component, which provides predictability and makes it easier to compose complex interfaces by passing values and callbacks from one component to another.

State (state) is an internal data to the component, mutable by specific functions (setState in classes, or useState in functions). Allows the interface to change dynamically based on user actions or other factors.

El Lifecycle A component's component describes the phases it goes through (assembly, update, and teardown). React offers different hooks and methods to execute code at each stage:

• componentDidMount o useEffect No dependencies: When mounting the component, useful for initialization or loading data.
• componentDidUpdate o useEffect with dependencies: When specific props or states change.
• componentWillUnmount or cleaning function in useEffect: Just before the component is destroyed, useful for cleaning up resources.

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Hooks: the revolution in React

The hooks They appeared in version 16.8 and marked a turning point in React development. They allow you to add state and lifecycle logic to functional components, which previously lacked these capabilities.

The most used are:

• useState: Allows you to declare state variables in functional components.
• useEffect: Runs functions after rendering and when dependencies change.
• useContext, useReducer, useCallback, useMemo, useRef: Other built-in hooks that help in different development situations.

There are some very strict rules For hook usage: they should only be called at the top level of a component function and never inside loops, conditionals, or nested functions.

Advantages and disadvantages of using React

React succeeds for many reasons:

• Easy to learn (if you are proficient in JavaScript and HTML), abundant documentation and many free and updated resources.
• Reusable components, which reduce repetitive code, improve organization and scalability.
• High performance thanks to the Virtual DOM and efficient rendering of only the changed parts.
• great community and ecosystem: countless libraries, tools and utilities to expand its possibilities.
• Stretch and compatible with many other technologies (such as Redux, Tailwind CSS, Firebase, Node.js).
• SEO friendly thanks to its server-side rendering (SSR) capabilities and frameworks like Next.js.

Its drawbacks include:

• Strong knowledge of modern JavaScript required.
• It only handles the view: you need to complement it with other libraries for more complex projects.
• In very large projects the application size may grow.

Why choose React over other alternatives?

React competes directly with frameworks like Angular and Vue. Its success is due to its combination of flexibility, performance, massive community, and ease of testing, debugging, and scaling applications. The fact that major companies like Facebook, Netflix, Airbnb, Uber, and Instagram have embraced React is a clear indicator of its robustness and reliability.

Furthermore, the fact that it is a view-oriented solution and not a complete framework gives the developer the freedom to choose the exact tools and add-ons that each project requires.

React use cases and practical applications

The real-world applications of React are virtually endless, but notable examples include:

• Dynamic web applications (Single Page Applications or SPA).
• Real-time chat and messaging systems.
• Social networks and community platforms.
• Cross-platform mobile apps (with React Native).
• Online stores and eCommerce solutions.
• Administration panels, dashboards and complex business applications.
• Task management, productivity, and calendar apps.
• On-demand music and video streaming platforms.

React Native: What makes it different from React?

React native React Native is a React-based framework that allows you to create native mobile applications using JavaScript and the same component philosophy. The key difference is that instead of rendering to HTML and web DOM, React Native translates components to native elements iOS and Android, facilitating the development of cross-platform mobile apps without sacrificing performance.

Although React and React Native share many common logic and syntax, each is tailored to its environment. React.js is primarily targeted at browsers, while React Native leverages APIs and controls specific to mobile operating systems.

The React ecosystem and community

One of the main drivers of React's growth has been its community. Thousands of developers contribute daily with libraries, solutions to common issues, tutorials, and improvements to the core and ecosystem.

Among the most popular libraries and tools in the ecosystem are:

• ReactRouter for routing and navigation between pages.
• Redux y Recoil for advanced global state management.
• Jest y enzymes for automated component testing.
• Babel for support for modern JavaScript and JSX.
• Webpack y Screw such as packaging and code optimization tools.

React's flexibility allows it to be combined with virtually any technology stack, both front- and back-end (Node.js, Firebase, etc.), and makes it easy to integrate styles (Sass, Tailwind, Bootstrap, etc.), graphics, forms, authentication, and more.

How to get started with React

To get started with React, you'll need basic knowledge of modern JavaScript (ES6), HTML, and CSS. It's recommended that you familiarize yourself with concepts like arrow functions, destructuring, modules, promises, and array methods.

The easiest way to create a React app is to use tools like Screw o Create React App. It is enough to have Node.js installed and run a few commands in the terminal:

• npx create-react-app my-app
• npm run start

This will generate the basic structure of the project, with folders like src for the source code and public for static files, and will allow you to see the result in the browser in a matter of seconds.

From there, you can create new components, import and organize code, add styles, install additional libraries, and deploy your app to specialized servers or hosting providers.

Major learning platforms and official React documentation offer tutorials, guides, examples, and resources to help everyone from beginners to experts get the most out of React.

As a tip: Take advantage of the community to find solutions to problems, discover best practices, and stay up-to-date on developments (such as the latest hooks, new methods, or licensing changes).

Working with React makes it easy to create modern and efficient interfaces, and its active and constantly growing community ensures a dynamic, collaborative, and evolving development environment. Learning React not only opens doors to numerous job opportunities and projects, but also gives you access to one of the most active and collaborative development communities today.