10 CSS Modules Best Practices

CSS Modules are a powerful tool for writing modular, reusable CSS code. They allow developers to write code that is more maintainable, scalable, and organized. However, there are some best practices that should be followed when using CSS Modules.

In this article, we will discuss 10 best practices for using CSS Modules. We will cover topics such as naming conventions, organization, and performance optimization. By following these best practices, you can ensure that your CSS Modules are well-structured and easy to maintain.

1. Use a naming convention

When you use a naming convention, it makes your code easier to read and understand. It also helps prevent conflicts between different stylesheets. For example, if two developers are working on the same project and they both name their classes “button”, then there will be a conflict when they try to merge their work together.

Using a consistent naming convention can help avoid this problem. A popular one is BEM (Block Element Modifier), which uses hyphens to separate class names into three parts: block, element, and modifier. This allows for more specific styling and better organization of your CSS modules.

2. Keep your CSS Modules small

By keeping your CSS Modules small, you can ensure that each module is focused on a single purpose. This makes it easier to maintain and debug the code since you don’t have to search through a large file for the relevant styles. Additionally, smaller modules are more reusable, which means they can be used in multiple places without having to rewrite them. Finally, smaller modules make it easier to keep track of changes as they’re made, so you can quickly identify any issues or bugs.

3. Avoid nesting selectors

When you nest selectors, it can lead to specificity issues. This means that the styles of a parent selector will override the styles of its child selector, even if they are conflicting.

To avoid this issue, use class names instead of nesting selectors. This way, each element has its own unique style and there is no risk of overriding any other elements’ styles. Additionally, using class names makes your code more readable and easier to maintain in the long run.

4. Don’t overuse global styles

Global styles are applied to all elements on the page, regardless of their class or ID. This can lead to unexpected results and make it difficult to debug issues.

Instead, use CSS modules to create specific classes for each element that you want to style. This will help keep your code organized and easier to maintain in the long run. Additionally, if you need to make changes to a particular element, you’ll know exactly which class to look for.

5. Use camel case for class names

Camel case is a naming convention that combines words together and capitalizes the first letter of each word. This makes class names easier to read, which can help developers quickly identify what classes are being used in their code. It also helps avoid conflicts with other CSS styles since it’s unlikely two different camel-cased class names will be the same.

Using camel case for class names also allows you to easily group related classes together. For example, if you have a class called “buttonPrimary” and another called “buttonSecondary”, they’ll both start with “button” so you know they’re related. This makes it easier to find and modify related classes when needed.

6. Make use of the :global() selector

The :global() selector allows you to write styles that are not scoped to the current module. This is useful when you want to apply a style across multiple modules, or if you need to override a style from an external library. By using this selector, you can ensure that your styles will be applied correctly and consistently throughout your application.

7. Use local scope to avoid conflicts

When you use global scope, all of your CSS classes are available to any component in the application. This can lead to conflicts between components if two or more components have the same class name. To avoid this issue, it’s best practice to use local scope for each component.

Local scope means that each component has its own set of unique class names and styles. This way, there is no risk of conflicting with other components. Additionally, using local scope makes it easier to maintain and debug your code since you know exactly which component a particular style belongs to.

8. Take advantage of composition

By composing your styles, you can create a more modular and maintainable codebase. This means that instead of writing all the styling for each component in one file, you can break it up into smaller pieces and compose them together to create a single style sheet.

This makes it easier to make changes to individual components without having to rewrite the entire style sheet. It also allows you to reuse existing styles across multiple components, which helps keep your code DRY (Don’t Repeat Yourself). Finally, composition makes it easier to debug issues since you can quickly identify where an issue is coming from.

9. Use @value and @composes

@value allows you to define a variable that can be used throughout your stylesheet. This makes it easier to maintain consistency and keep code DRY (Don’t Repeat Yourself). For example, if you have multiple elements with the same color, you can use @value to set the color once and then reference it in each element’s style definition.

@composes is another useful feature of CSS Modules. It allows you to compose classes together so that they share the same properties. This helps reduce repetition and keeps your codebase more organized. For instance, if you have two classes that both need the same font-size property, you can use @composes to combine them into one class.

10. Prefer BEM syntax

BEM stands for Block, Element, Modifier and it’s a way of writing CSS classes that makes them more readable and easier to maintain.

BEM syntax is especially useful when using CSS Modules because it helps you keep track of which styles are being applied to which elements. It also allows you to easily identify the purpose of each class, making it easier to debug any issues that may arise.

Finally, BEM syntax can help you avoid naming conflicts between different modules, as well as make your code more reusable across projects.