Naming conventions in CSS - Mini Project: Build & Apply

CSS Naming Conventions with BEM

📖 Scenario: You are creating a simple webpage section with a card component. To keep your CSS organized and easy to maintain, you will use a naming convention called BEM (Block Element Modifier).

🎯 Goal: Build CSS classes using the BEM naming convention for a card component with a title, description, and a button.

📋 What You'll Learn

Create a CSS block class named card.

Add element classes for title, description, and button inside the card block using BEM syntax.

Add a modifier class for the button to indicate a primary style using BEM syntax.

Use simple CSS properties to style each class so the difference is visible.

💡 Why This Matters

🌍 Real World

Using naming conventions like BEM helps teams write CSS that is easy to understand and maintain, especially in large projects with many components.

💼 Career

Front-end developers often use BEM or similar conventions to keep styles organized and avoid conflicts, making this skill valuable for professional web development.

1

Create the BEM block class

Create a CSS class called .card that sets background-color to #f0f0f0 and padding to 1rem.

CSS

/* Your code here */

Hint

Use a CSS class selector .card and add the properties inside curly braces.

2

Add BEM element classes

Add CSS classes .card__title, .card__description, and .card__button. Set font-weight to bold for .card__title, font-size to 1rem for .card__description, and padding to 0.5rem 1rem for .card__button.

CSS

.card {
  background-color: #f0f0f0;
  padding: 1rem;
}
/* Your code here */

Hint

Use double underscores __ to separate block and element names in BEM.

3

Add a BEM modifier class

Add a CSS class .card__button--primary that sets background-color to #007bff and color to #fff.

CSS

.card {
  background-color: #f0f0f0;
  padding: 1rem;
}
.card__title {
  font-weight: bold;
}
.card__description {
  font-size: 1rem;
}
.card__button {
  padding: 0.5rem 1rem;
}
/* Your code here */

Hint

Use double hyphens -- to add a modifier to the element in BEM.

4

Complete with responsive font size

Add a media query for screens smaller than 600px that sets font-size of .card__description to 0.875rem.

CSS

.card {
  background-color: #f0f0f0;
  padding: 1rem;
}
.card__title {
  font-weight: bold;
}
.card__description {
  font-size: 1rem;
}
.card__button {
  padding: 0.5rem 1rem;
}
.card__button--primary {
  background-color: #007bff;
  color: #fff;
}
/* Your code here */

Hint

Use a media query with max-width: 600px and place the CSS rule inside its block.

Practice

1. Which of the following is the best practice for naming CSS classes?

easy

A. Use camelCase, like mainHeader.

B. Use uppercase letters and underscores, like Main_Header.

C. Use lowercase letters and hyphens to separate words, like main-header.

D. Use spaces between words, like main header.

Solution

1. Step 1: Understand common CSS naming styles

   CSS classes should be easy to read and consistent. Lowercase with hyphens is widely accepted.

2. Step 2: Compare options

   Use lowercase letters and hyphens to separate words, like main-header. uses lowercase and hyphens, which is recommended. Options B and C use uppercase or camelCase, less common in CSS. Use spaces between words, like main header. uses spaces, which is invalid in class names.

3. Final Answer:

   Use lowercase letters and hyphens to separate words, like main-header. -> Option C

4. Quick Check:

   Lowercase + hyphens = best CSS naming [OK]

Hint: Use lowercase and hyphens for CSS classes [OK]

Common Mistakes:

• Using spaces in class names
• Using uppercase letters
• Using camelCase instead of hyphens

2. Which CSS class name follows the BEM naming convention?

easy

A. button--primary

B. button_primary

C. buttonPrimary

D. button primary

Solution

1. Step 1: Recall BEM naming rules

   BEM uses block__element--modifier format. Double hyphens separate modifiers.

2. Step 2: Identify correct format

   button--primary uses double hyphens for modifier --primary, matching BEM. Options A and B use camelCase or underscores, not BEM. button primary uses space, invalid in class names.

3. Final Answer:

   button--primary -> Option A

4. Quick Check:

   BEM modifier uses double hyphens [OK]

Hint: BEM modifiers use double hyphens (--modifier) [OK]

Common Mistakes:

• Using underscores instead of hyphens
• Using camelCase for BEM
• Using spaces in class names

3. Given this CSS class name: card__title--large, what does it represent in BEM?

medium

A. Block: card, Modifier: title, Element: large

B. Modifier: card, Block: title, Element: large

C. Element: card, Block: title, Modifier: large

D. Block: card, Element: title, Modifier: large

Solution

1. Step 1: Break down the BEM parts

   In card__title--large, card is the block, title is the element (after double underscore), and large is the modifier (after double hyphen).

2. Step 2: Match parts to options

   Block: card, Element: title, Modifier: large correctly identifies block, element, and modifier. Other options mix these parts incorrectly.

3. Final Answer:

   Block: card, Element: title, Modifier: large -> Option D

4. Quick Check:

   BEM = block__element--modifier [OK]

Hint: BEM: block__element--modifier order [OK]

Common Mistakes:

• Confusing element and modifier positions
• Mixing block and element names
• Ignoring double underscores and hyphens

4. Identify the error in this CSS class name: nav__item_active

medium

A. Class name is too long

B. Underscore used instead of double hyphen for modifier

C. Spaces are used instead of underscores

D. Double underscore missing between block and element

Solution

1. Step 1: Check BEM syntax

   BEM requires modifiers to be separated by double hyphens --, not underscores.

2. Step 2: Analyze the class name

   The class nav__item_active uses a single underscore for the modifier, which is incorrect. It should be nav__item--active.

3. Final Answer:

   Underscore used instead of double hyphen for modifier -> Option B

4. Quick Check:

   Modifier separator = double hyphen [OK]

Hint: Modifiers need double hyphens, not underscores [OK]

Common Mistakes:

• Using single underscore for modifiers
• Forgetting double underscore between block and element
• Using spaces in class names

5. You want to create CSS classes for a card component with a title and a highlighted state using BEM. Which naming set is correct?

hard

A. card, card__title, card--highlighted

B. card, card_title, card_highlighted

C. card, card-title, card-highlighted

D. card, card__title--highlighted, card__highlighted

Solution

1. Step 1: Understand BEM structure for blocks, elements, and modifiers

   Block is card. Element is card__title. Modifier on block is card--highlighted.

2. Step 2: Evaluate options

   card, card__title, card--highlighted correctly uses BEM naming. card, card_title, card_highlighted uses underscores, not BEM. card, card-title, card-highlighted uses hyphens but not BEM format. card, card__title--highlighted, card__highlighted incorrectly applies modifier to element and duplicates modifier.

3. Final Answer:

   card, card__title, card--highlighted -> Option A

4. Quick Check:

   BEM block, element, modifier naming [OK]

Hint: BEM: block, block__element, block--modifier [OK]

Common Mistakes:

• Using underscores instead of BEM separators
• Applying modifiers to elements incorrectly
• Mixing hyphen and underscore styles