The Many Ways to Include CSS in JavaScript Applications

In front-end development, the handling of CSS has always been controversial. This article discusses several common CSS architecture methods and analyzes their advantages and disadvantages, emphasizing that there are no absolute advantages and disadvantages, and the choice needs to be determined based on the actual situation of the project.

First, let’s look at the most traditional method: external style sheets .

pass<link> Tags introduce external CSS files:

<link href="styles.css" rel="stylesheet">

This approach is simple and straightforward, but for large and complex projects, maintaining a single style sheet can become difficult, CSS code is prone to redundant, and can create style conflicts. Although it can be improved with tools like Sass or PostCSS, it is still the end of the day a large CSS file that can cause render blockage and slow loading. However, for teams with insufficient experience in small projects or front-end development, this approach is easy to understand and has high browser caching efficiency.

To resolve style conflict issues, we can adopt CSS Modules .

CSS Modules avoids style conflicts by generating component-specific class names, such as header__2lexd . This ensures the locality of the style, but also limits the use of global styles. The :global pseudo-class is needed to define the global style, which needs to be handled with caution to avoid too many global styles affecting maintainability. Here is an example of using CSS Modules in a React component:

 // ./css/Button.css
.btn { /* ... */ }

// ./Button.js
import styles from "./css/Button.css";
// ... Use styles.btn ...

CSS Modules can also be used in conjunction with preprocessors such as Sass and Less. It is suitable for projects that require local style and focus on performance.

Next is CSS-in-JS .

CSS-in-JS writes CSS code directly into JavaScript. Commonly used libraries include JSS, Emotion, and Styled Components. It usually generates CSS code with only the current rendering component and inserts it into This enables on-demand loading, avoid render blocking, and improves performance. At the same time, it also allows dynamic generation of styles based on component state and supports advanced features such as theme. However, it can also cause JavaScript files to be too large and blur the boundaries between business logic and styles. An example of a React component using Styled Components:

 // ./Button.js
import styled from 'styled-components';

const StyledButton = styled.button` /* ... */ `;
// ... Using StyledButton ...

Finally, let’s summarize: External stylesheets, CSS Modules, and CSS-in-JS each have their own advantages and disadvantages. Which method to choose depends on the project size, team technical level and performance requirements. It is important to choose a plan that suits the needs of the project and establish a clear style architecture to ensure the long-term maintainability of the project. There is no perfect solution, only the most suitable one.

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