CSS in JS: Unleashing the Power of JavaScript for Styling

Maheen Waris | Oct 5, 2023 min read

Understanding CSS in JS

CSS-in-JS is a styling approach that allows developers to write CSS styles using JavaScript. Instead of creating separate CSS files, developers can define styles directly within their JavaScript code. This approach has several advantages:

  1. Scoped Styles: CSS-in-JS libraries generate scoped styles, which means that styles only affect the components they are associated with. This eliminates global scope issues commonly found in traditional CSS.
  2. Dynamic Styles: JavaScript can be used to generate styles dynamically based on various factors, such as user interactions or data from an API. This makes it easier to create responsive and interactive user interfaces.
  3. Better Developer Experience: Developers can use JavaScript’s powerful features, including variables and functions, to manage styles, resulting in a more maintainable codebase.
  4. Performance Optimization: Some CSS-in-JS libraries generate optimized, minimal CSS, reducing the overall page load time by serving only the styles needed for a specific component or page.
  1. Styled-components: Styled-components is one of the most popular CSS-in-JS libraries. It allows developers to write CSS styles using tagged template literals in JavaScript. Styles are encapsulated within components, ensuring that they don’t leak to other parts of the application.
  2. Emotion: Emotion is another widely used CSS-in-JS library known for its high performance and small bundle size. It provides a flexible and expressive API for defining styles in JavaScript, making it easy to create responsive and dynamic designs.
  3. JSS (JavaScript Stylesheets): JSS is a versatile CSS-in-JS library that supports various stylesheet formats, including plain objects, function values, and JSON. It integrates seamlessly with popular JavaScript frameworks like React.
  4. Glamorous: Glamorous is a CSS-in-JS library that focuses on a simple and intuitive API for styling components. It provides an elegant way to create reusable styles in JavaScript.

Benefits of CSS-in-JS Libraries

  1. Improved Isolation: CSS-in-JS libraries ensure that styles are scoped to their respective components, reducing the chances of unintended style conflicts. This makes it easier to maintain and refactor code.
  2. Dynamic Theming: Creating dynamic themes and styles based on user preferences or application state is straightforward with CSS-in-JS libraries. This enables the development of applications with customizable appearances.
  3. Optimized Performance: Many CSS-in-JS libraries generate optimized stylesheets, resulting in faster load times and improved application performance. Unused styles are often removed from the final output.
  4. Easy Maintenance: Managing and refactoring styles becomes more manageable since styles are closely tied to their corresponding components. Developers can easily locate and update styles as needed.

Challenges and Considerations

While CSS-in-JS libraries offer numerous advantages, they may not be the best choice for every project. Here are some considerations and challenges:

  1. Learning Curve: Developers who are familiar with traditional CSS might need some time to adapt to the JavaScript-based approach.
  2. Bundle Size: Depending on the library and configuration, CSS-in-JS solutions can contribute to larger bundle sizes. Careful optimization is necessary to mitigate this issue.
  3. Tooling: Integrating CSS-in-JS libraries into existing toolchains may require some adjustments. Developers should ensure compatibility with their build tools and development workflows.


CSS-in-JS libraries have redefined the way we approach styling in web development. They offer benefits like improved isolation, dynamic theming, and optimized performance, making them a compelling choice for modern web applications. While they come with a learning curve and some challenges, the advantages they offer in terms of maintainability and developer experience are worth exploring. Whether you choose styled-components, Emotion, JSS, or another library, incorporating CSS-in-JS into your project can lead to more efficient and responsive web applications.