What is React? A Beginner's Guide

React is a JavaScript library that has transformed the way user interfaces (UI) are developed in web applications. Since its release by Facebook in 2013, it has gained popularity among developers and companies due to its flexibility and performance. In this guide, we will explore what React is, its main features, and how you can start using it in your projects.

History of React

Before delving into how React works, it is important to understand its historical context. The need for a library like React arose when web applications began to become more complex. Facebook needed an efficient way to manage the UI of its applications, and as a result, React was created. Since then, it has remained one of the most relevant tools in web development.

Why Choose React?

Choosing React for web application development comes with multiple advantages. Here are some of them:

1. Reusable Components

React is based on the concept of components. This means you can create small code snippets that represent parts of the user interface, and then reuse them throughout the application. This not only saves time but also improves the maintainability of the code.

2. Virtual DOM

One of the most notable features of React is its Virtual DOM. Unlike the traditional DOM, the Virtual DOM allows React to manage UI changes more efficiently. When data changes, React updates the Virtual DOM and then compares the changes with the real DOM only when necessary, making applications faster.

3. Unidirectional Data Flow

React uses a unidirectional data flow, which means data flows in one direction, from parent components to child components. This makes it easier to track data and minimizes the risks of errors caused by unexpected changes in the UI.

4. Organized Ecosystem

React does not operate in isolation; it has a rich ecosystem of libraries and tools. From React Router for managing navigation to Redux for state management, developers have a variety of resources at their disposal that facilitate the development of complex applications.

How Does React Work?

Next, we will break down some of the key concepts you need to know to understand how React works.

1. JSX: JavaScript XML

React uses JSX, an extension of JavaScript that allows you to write HTML code within JavaScript. This makes it easier to create interactive components since you can combine logic and structure in the same place.

const element = <h1>Hello, world!</h1>;

2. Functional and Class Components

There are two main types of components in React: functional and class components.

Functional Components: These are simpler and are primarily used when there is no need to manage state.

function MyComponent() {
    return <h1>Hello from a functional component!</h1>;
}

Class Components: These allow for managing internal state and can contain lifecycle methods.

class MyComponent extends React.Component {
    render() {
        return <h1>Hello from a class component!</h1>;
    }
}

3. Props and State

Components in React can receive props (properties) that allow them to receive data from their parent components. The state is an object that stores data that affects the component's behavior and rendering.

class MyCounter extends React.Component {
    constructor() {
        super();
        this.state = { counter: 0 };
    }

    increment = () => {
        this.setState({ counter: this.state.counter + 1 });
    }

    render() {
        return (
            <div>
                <h1>{this.state.counter}</h1>
                <button onClick={this.increment}>Increment</button>
            </div>
        );
    }
}

Getting Started with React

To start using React, follow these steps:

1. Install Node.js and npm

First, download and install Node.js on your system. npm (Node Package Manager) is automatically installed with Node.js and is necessary for managing your project's dependencies.

2. Create a New Project

You can create a new React project using Create React App, an official tool that simplifies the setup of your development environment.

npx create-react-app my-app
cd my-app
npm start

3. Project Structure

Once you have created your application, get familiar with its folder structure. The most relevant files include:

src/: Where the source code of your application resides.
public/: Contains static files that are served directly to the browser.

4. Build Your First Application

Start by building your first component and adding it to the application. You can edit the App.js file in the src folder to insert your component:

function App() {
    return (
        <div className="App">
            <MyCounter />
        </div>
    );
}

Conclusion

React has revolutionized the development of user interfaces in web applications, offering an efficient and flexible way to build reusable components. With its robust ecosystem and active community, learning React can open many doors in the world of web development.

If you follow this guide and practice with simple projects, you will be well on your way to becoming a competent React developer. Don't hesitate to explore the official documentation and participate in communities to continue learning!