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CSS Modules

Learn to create local class names with CSS Modules.

CSS Modules

CSS Modules scope styles to a component. The file is named Button.module.css; on import you get an object: import styles from "./Button.module.css".

You apply a class with className={styles.btn}. The bundler generates a unique name for each class, so there is no clash.

This method is the standard way to write safe styles in big projects.

Scoped class names

Modules turns a simple name like .btn into a unique name like Button_btn__x7y2. You do not write this name; the bundler generates it.

So even if two components both have .btn, they do not clash. This is the basis of scalable styling.

You can use camelCase class names: styles.primaryBtn.

Practice Modules button

Complete the skeleton. Write a PrimaryButton component; import the styles object from "./PrimaryButton.module.css". Return <button className={styles.primary}>Send</button>. Export it.

Starter code

App.jsx
// Define PrimaryButton here

// remember to import styles

Sample solution

App.jsx
import styles from "./PrimaryButton.module.css";

function PrimaryButton() {
  return <button className={styles.primary}>Send</button>;
}

export default PrimaryButton;

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 How does a CSS Modules file name end?

App.jsx
The bundler scopes based on the suffix.
  • .css
  • .style
  • .scss
  • .module.css Correct answer

Explanation: The .module.css suffix marks it as a module.

2 CSS Modules: fill in the missing part

Question 
className={____}
Answer 
className={styles.btn}

Explanation: You took the class from the styles object.

3 CSS Modules: match the terms

Term Meaning
.module.css Modules suffix
styles.btn Class usage
unique name No clash
camelCase Naming

All lessons in Beginner

1 React intro

  1. What is React?
  2. Setup and Vite
  3. Your first component
  4. Summary - React intro

2 JSX basics

  1. What is JSX?
  2. Expressions and curly braces
  3. Attributes and className
  4. Summary - JSX basics

3 Components

  1. Component logic
  2. Component tree
  3. Naming rules
  4. Summary - Components

4 Profile card

  1. Project: Profile card
  2. Avatar component
  3. Info list
  4. Assemble the card

5 Props

  1. What are props?
  2. Reading props
  3. Children prop
  4. Default props
  5. Summary - Props

6 Conditional rendering

  1. What is conditional rendering?
  2. Ternary operator
  3. Logical AND (&&)
  4. Early return
  5. Summary - Conditional rendering

7 List rendering

  1. What is list rendering?
  2. The key attribute
  3. Array to components
  4. Filtering and sorting
  5. Summary - List rendering

8 Shopping list

  1. Project: Shopping list
  2. Item component
  3. List body
  4. Empty state

9 Events

  1. Events
  2. The event object
  3. Form events
  4. Summary - Events

10 useState

  1. What is state?
  2. The useState call
  3. Updating state
  4. Multiple state values
  5. Summary - useState

11 Counter app

  1. Project: Counter app
  2. Number and buttons
  3. Decrement and reset
  4. Boundary control

12 Forms

  1. Controlled input
  2. Form submission
  3. Multiple fields
  4. Summary - Forms

13 Styling

  1. Styling with CSS
  2. CSS Modules
  3. Inline styles
  4. Summary - Styling

14 styled-components

  1. What is styled-components?
  2. Styling with props
  3. Using themes
  4. Summary - styled-components

15 useReducer

  1. What is useReducer?
  2. Action and state
  3. useState vs useReducer
  4. Summary - useReducer

16 useEffect

  1. What is useEffect?
  2. Dependency array
  3. Cleanup function
  4. Summary - useEffect

17 Context

  1. What is context?
  2. createContext
  3. Provider and useContext
  4. Summary - Context

18 useRef

  1. What is useRef?
  2. DOM access
  3. Timer example
  4. Summary - useRef

19 Todo app

  1. Project: Todo app
  2. Todo entry form
  3. Todo list
  4. Filter and summary

20 Beginner final

  1. Challenge: Weather card
  2. Challenge: Cart summary
  3. Challenge: Counter and reset
  4. Challenge: Dropdown menu