CSS Modules in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the CSS module correctly in a Next.js component.

NextJS

import styles from '[1]';

export default function Button() {
  return <button className={styles.btn}>Click me</button>;
}

Drag options to blanks, or click blank then click option'

A'./button.css'

B'./Button.module.css'

C'./styles.css'

D'./Button.css'

Attempts:

3 left

💡 Hint

Common Mistakes

Importing a regular CSS file without .module in the name.

Using wrong file path or extension.

You must import the CSS module file with the exact module name ending in .module.css to use CSS Modules in Next.js.

2fill in blank

medium

Complete the code to apply a CSS module class to a div element.

NextJS

export default function Card() {
  return <div className=[1]>Content</div>;
}

Drag options to blanks, or click blank then click option'

Astyles.card

Bstyles['card']

C"card"

Dcard

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain string class names without referencing the styles object.

Using incorrect syntax like just the class name without quotes or styles.

Use styles.card to apply the CSS module class named card to the element.

3fill in blank

hard

Fix the error in the code to correctly apply multiple CSS module classes to a button.

NextJS

export default function SubmitButton() {
  return <button className={`$[1] ${styles.primary}`}>Submit</button>;
}

Drag options to blanks, or click blank then click option'

Astyles['btn']

Bbtn

Cstyles.btn

Dbtn.primary

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain class names without styles. prefix inside template strings.

Trying to access classes as plain strings or invalid object properties.

Use styles.btn to correctly reference the CSS module class for btn inside the template string.

4fill in blank

hard

Fill both blanks to create a CSS module style object with dynamic class names.

NextJS

const buttonClass = `$[1] [2]`;

export default function Button() {
  return <button className={buttonClass}>Press</button>;
}

Drag options to blanks, or click blank then click option'

Astyles.btn

Bstyles.active

Cbtn

Dactive

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain class names without styles. prefix.

Forgetting to separate class names with a space.

Use styles.btn and styles.active to combine CSS module classes dynamically.

5fill in blank

hard

Fill all three blanks to create a CSS module style object with conditional class names.

NextJS

const isActive = true;
const className = `$[1] $[2] ? [3] : ''`;

export default function Toggle() {
  return <div className={className}>Toggle me</div>;
}

Drag options to blanks, or click blank then click option'

Astyles.toggle

BisActive

Cstyles.active

Dactive

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain strings instead of CSS module references.

Not using the boolean variable correctly in the condition.

Use styles.toggle as the base class, check the isActive boolean, and conditionally add styles.active if true.

Practice

1. What is the main benefit of using CSS Modules in a Next.js project?

easy

A. They enable global CSS styles to override component styles.

B. They automatically minify CSS files for faster loading.

C. They scope CSS styles locally to components, avoiding conflicts.

D. They allow CSS to be written inside JavaScript files only.

Solution

1. Step 1: Understand CSS Modules purpose

   CSS Modules scope CSS locally to components, so styles don't leak or conflict.

2. Step 2: Compare options with this purpose

   Only They scope CSS styles locally to components, avoiding conflicts. describes this key benefit. Others describe unrelated features.

3. Final Answer:

   They scope CSS styles locally to components, avoiding conflicts. -> Option C

4. Quick Check:

   CSS Modules = Local scoped styles [OK]

Hint: Remember: CSS Modules isolate styles per component [OK]

Common Mistakes:

• Thinking CSS Modules minify CSS automatically
• Confusing CSS Modules with CSS-in-JS
• Believing CSS Modules create global styles

2. Which of the following is the correct way to import a CSS Module file named Button.module.css in a Next.js component?

easy

A. import styles from './Button.css';

B. import styles from './Button.module.css';

C. import './Button.module.css';

D. import styles from './Button.cssmodule';

Solution

1. Step 1: Identify correct file extension for CSS Modules

   Next.js requires CSS Modules files to end with .module.css.

2. Step 2: Check import syntax

   Importing with import styles from './Button.module.css'; correctly imports the module as an object.

3. Final Answer:

   import styles from './Button.module.css'; -> Option B

4. Quick Check:

   Import CSS Modules with .module.css and assign to variable [OK]

Hint: Always use .module.css extension and import with 'from' [OK]

Common Mistakes:

• Using wrong file extension like .css or .cssmodule
• Importing without assigning to a variable
• Forgetting the .module part in filename

3. Given the CSS Module styles.module.css with content:

.title { color: red; }

And the React component:

import styles from './styles.module.css';

export default function Header() {
  return <h1 className={styles.title}>Hello</h1>
}

What color will the <h1> text be when rendered?

medium

A. Red

B. Black (default)

C. Blue

D. Green

Solution

1. Step 1: Check CSS Module style for .title

   The CSS sets .title color to red.

2. Step 2: Confirm component uses styles.title as className

   The component applies className={styles.title}, so the red color applies.

3. Final Answer:

   Red -> Option A

4. Quick Check:

   CSS Module class applied = red text [OK]

Hint: ClassName from styles object applies CSS Module styles [OK]

Common Mistakes:

• Assuming default black color without checking CSS
• Confusing CSS Modules with global CSS
• Not using styles.title but a string instead

4. What is wrong with this Next.js component using CSS Modules?

import styles from './Card.module.css';

export default function Card() {
  return <div className="styles.card">Content</div>
}

medium

A. The component must be a class component to use CSS Modules.

B. The CSS file should be imported with a different name.

C. The CSS Module file must be named Card.css, not Card.module.css.

D. The className should use curly braces, not quotes, to apply styles.card.

Solution

1. Step 1: Identify how className is assigned

   The code uses className="styles.card", which is a string literal, not the variable.

2. Step 2: Correct syntax for applying CSS Module class

   It should be className={styles.card} to use the imported styles object.

3. Final Answer:

   The className should use curly braces, not quotes, to apply styles.card. -> Option D

4. Quick Check:

   Use curly braces to apply CSS Module classes [OK]

Hint: Use {styles.className}, not "styles.className" for CSS Modules [OK]

Common Mistakes:

• Using quotes instead of curly braces for className
• Renaming CSS Module file incorrectly
• Thinking CSS Modules require class components

5. You want to style a Next.js component with two CSS Module classes: primary and large from Button.module.css. Which is the correct way to apply both classes to a <button> element?

hard

A. Click

B. Click

C. Click

D. Click

Solution

1. Step 1: Understand how to combine multiple CSS Module classes

   Use template literals or string concatenation to combine classes as strings.

2. Step 2: Evaluate each option

   Click uses template literals correctly to combine classes with a space.
   Click uses a string literal, so classes won't apply.
   Click concatenates without space, merging class names incorrectly.
   Click passes an array, which React does not accept as className.

3. Final Answer:

   <button className={`${styles.primary} ${styles.large}`}>Click</button> -> Option A

4. Quick Check:

   Combine CSS Module classes with template literals [OK]

Hint: Use backticks and ${} to combine multiple CSS Module classes [OK]

Common Mistakes:

• Using quotes instead of variables for className
• Concatenating without spaces between classes
• Passing arrays directly to className