A Short Introduction to React
Tags: react, javascript, webdev
Published: 2023-02-13 09:13:07

React is a JavaScript library for building user interfaces. It is developed and maintained by Facebook, and is widely used for building single-page applications and mobile apps. React allows developers to build reusable UI components, manage the state of the application, and efficiently render changes to the user interface.

### Why use react?

One reason is **reusability**. In react, you can create components that you can reuse in different places. This helps to keep your code organized and maintainable.

React uses a **virtual DOM**, which allows it to update the user interface efficiently. The virtual DOM optimizes updates to the user interface by minimizing the number of actual DOM updates required, resulting in improved performance.

React has a large and active community, which means that there are many resources available to learn from and get help with. It is also compatible with a variety of tools and libraries, making it easier to build complex and feature-rich applications.

> "Reusability, Performance and Large Active Community"

### What is JSX?

JSX is a syntax extension for JavaScript that allows you to write HTML-like code within your JavaScript files.

```javascript
export default function HelloWorld() {
  const message = "World"
  return (
    <div>
      <h1>Hello, {message}!</h1>
    </div>
  );
}
```

As you can see, the above code returns a function called `HelloWorld`, but notice how we are returning some HTML elements. That's JSX. This allows us to combine HTML and JavaScript effortlessly.

### Virtual DOM

Virtual DOM (VDOM) is a concept used in libraries like React to update user interfaces efficiently. The Virtual DOM is an in-memory representation of the actual DOM, the structure that represents the elements and content of a web page.

When changes are made to the user interface, React updates the Virtual DOM first, and then calculates the difference between the old Virtual DOM and the new Virtual DOM. This calculation determines the most efficient way to update the actual DOM, reducing the amount of work required to make the updates.

By using the Virtual DOM, React can optimize updates to the user interface and minimize the number of updates to the actual DOM, resulting in improved performance. This makes it possible to build fast, dynamic user interfaces with a high level of interactivity and responsiveness.

> In summary, the Virtual DOM is a powerful concept used by libraries like React to efficiently update user interfaces and provide a high level of performance.

### What is SPA?

A single-page application (SPA) is a web application or website that interacts with the user by dynamically rewriting the current page, instead of loading entire new pages from a server. This provides a more fluid and responsive user experience, as the application only has to load the necessary data and update specific parts of the page, instead of reloading the entire page.

In a single-page application, the majority of the application logic runs on the client side (in the user's browser), instead of on the server. This allows for fast and smooth updates to the user interface, as there is no need to wait for data to be sent back and forth between the client and server. React is well-suited for building SPAs.