Qué es CSS-in-JS

What is CSS in JS and why doesn't it replace regular CSS?

CSS in JS is an innovative way of writing CSS styles using JavaScript. While many may question whether this approach could ever replace traditional CSS, the categorical answer is no. CSS in JS ultimately generates normal CSS; however, the way we write it and integrate it with the component logic of an application is different. By using CSS in JS, we can enhance the benefits of working with components in our application, taking full advantage of JavaScript's functionality to create dynamic and efficient styles.

How do we integrate CSS in JS into our projects?

Historically, the standard approach has been to create .css style sheets and link them to our HTML documents. Alternatively, we can also employ inline styles or the use of <style> tags. However, the trend has evolved, integrating preprocessors and postprocessors for even more efficiency.

• Preprocessors such as Sass or Less facilitate the use of variables, functions and other programmatic elements in CSS style.
• Postprocessors such as PostCSS allow us to use future CSS features, ensuring that the browser understands them immediately.

With the rise of components, applications are being broken down into smaller parts, making them easier to maintain and expand with new functionality. CSS in JS integrates styles directly within components, adding not only organization but also the potential of JavaScript to create more complex and dynamic styles.

How do we implement CSS in JS with Style Components in React?

Let's look at an example using Style Components, a popular way of working with CSS in JS within the React ecosystem. Here we define a component called Title:

`import styled from 'styled-components';
const Title = styled.h2`
 color: white; font-size: 60px; `;

This syntax is familiar from normal CSS. The big difference is that we specify that when we want to apply certain styles, we use the Title component instead of defining styles for all <h2> in the application.

How do we make use of CSS dynamics in JS?

Implementing CSS dynamics in JS is simple. Suppose we want to change the color of the title depending on whether there is an error:

const Title = styled.h2`
 color: ${(props) => (props.error ? 'red' : 'white')}; `;

When we use the Title component and pass the error attribute, the color will change to red. Otherwise, it will be white. This is just a sample of how we can apply JavaScript logic to our styles, taking advantage of props and the context of entire applications.

How to handle global CSS styles in JS?

A common myth is that CSS in JS does not allow writing global styles. However, CSS in JS tools such as Style Components enable the creation of global styles for general tags, certain class selectors, or basic elements such as the body. This ensures that, even using CSS in JS, we can maintain the need to apply styles to application-wide elements without complications.

As you can see, CSS in JS not only keeps the essence of traditional CSS alive, but expands its horizons by integrating the programmatic capabilities of JavaScript to provide a more robust development experience. This approach is ideal when working with modern frameworks and components, favoring a more customizable and dynamic set of styling features. Get your code editor ready and delve into the classes in this module to explore the possible applications of this knowledge - continue to learn and revolutionize your development experience!