What is the purpose of CSS-in-JS libraries in React?

CSS-in-JS libraries in React help you to write and manage styles for your components directly within JavaScript files. This approach offers several advantages over traditional methods of styling in web development, where CSS is typically written in separate files and then linked to HTML.

Main purposes & benefits of using CSS-in-JS libraries in React:

• Scoped Styles: CSS-in-JS libraries enable the creation of scoped styles for React components. The styles are encapsulated within the component, reducing the likelihood of naming conflicts and unintended side effects. This makes it easier to manage styles in large codebases with numerous components.
• Component-Based Styling: With CSS-in-JS, styling is closely tied to individual components. This aligns well with the component-based architecture of React, making it more intuitive for developers to associate styles with specific components. It encourages a modular and reusable approach to styling.
• Dynamic and Conditional Styling: JavaScript’s dynamic nature allows for the generation of styles based on dynamic data or component state. CSS-in-JS libraries make it easier to apply conditional styles, respond to user interactions, or dynamically adjust styles based on changing application states.
• Elimination of Global Scope Issues: Traditional CSS can lead to global scope issues and unintended style overrides. CSS-in-JS libraries help mitigate this problem by encapsulating styles within components, reducing the risk of conflicts between different parts of the application.
• Theme and Variants Support: CSS-in-JS libraries often provide built-in support for theming and defining style variants. This allows for consistent theming across the application and makes it straightforward to create variations of components with different styles.

Popular CSS-in-JS libraries in the React ecosystem include styled-components, Emotion, and JSS (JavaScript Style Sheets), each with its own syntax and features. The choice of library often depends on the specific needs and preferences of the development team.