BEM vs CSS Modules: What are the differences?

Introduction

In web development, there are various approaches to structuring and styling CSS code. Two popular approaches are the Block Element Modifier (BEM) methodology and CSS Modules. This markdown will highlight key differences between BEM and CSS Modules.

1. Code Organization: BEM focuses on naming conventions to organize code, where each class describes a specific block element or modifier. CSS Modules, on the other hand, uses modularization to encapsulate styles within specific components, providing a more component-based approach.

2. Namespace Conflicts: BEM uses specific naming conventions that reduce the likelihood of naming conflicts. Each BEM class name is unique and self-contained. CSS Modules generate unique class names for each component, avoiding conflicts by scope, as the styles are locally scoped to the component without the need for long class names.

3. Dependency Management: BEM usually relies on manual dependency management, where you have to explicitly include all the necessary CSS classes in the HTML markup. CSS Modules, however, automatically handles dependencies by importing and including the required styles in the component file.

4. Module Reusability: BEM promotes reusability by separating structure and style. Styles can be applied to different elements with the same BEM class, allowing for modular and reusable components. CSS Modules, on the other hand, encapsulate styles within components, often resulting in less reusability as the styles are tighter to the component itself.

5. Global vs Local Scope: BEM classes have global scope and can be applied to any element within the project. This provides flexibility but can also lead to unintended style conflicts. CSS Modules, on the other hand, have local scope, meaning styles are only applied within the component they are imported into, reducing the chances of style conflicts.

6. Class Naming Convention: BEM follows a specific class naming convention, where each class represents a block, element, or modifier. This structured naming convention helps developers identify the purpose of each class. CSS Modules do not enforce a specific naming convention, allowing developers more freedom and flexibility in naming classes.

In summary, while BEM focuses on naming conventions and global scope, CSS Modules provide modularization and local scope. BEM promotes reusability through structured class names, while CSS Modules encapsulate styles within components. The choice between BEM and CSS Modules depends on the specific project requirements and the desired approach to code organization and styling.