BEM Naming Convention: Brief Guide

🎯 What is BEM?

BEM stands for Block Element Modifier - a CSS naming methodology that creates clear, maintainable CSS class names.

📝 BEM Syntax

/* Block */
.block {}

/* Element */
.block__element {}

/* Modifier */
.block--modifier {}
.block__element--modifier {}

🧱 The Three Parts

Block (Component)

Independent, reusable component:

.card {}
.button {}
.navigation {}
.search-form {}

Element (Part of Block)

Uses double underscore __:

.card__header {}
.card__title {}
.card__body {}
.button__icon {}
.button__text {}

Modifier (Variation)

Uses double dash --:

.button--primary {}
.button--large {}
.card--featured {}
.card__header--dark {}

💡 Real Example

<!-- HTML -->
<div class="card card--featured">
  <header class="card__header card__header--dark">
    <h2 class="card__title">Featured Article</h2>
  </header>
  <div class="card__body">
    <p class="card__text">Article content...</p>
  </div>
  <footer class="card__footer">
    <button class="button button--primary button--large">
      <span class="button__icon">📖</span>
      <span class="button__text">Read More</span>
    </button>
  </footer>
</div>

/* CSS */
.card {
  padding: 1rem;
  border-radius: 8px;
  background: white;
}

.card--featured {
  border: 2px solid #007bff;
}

.card__header {
  margin-bottom: 1rem;
}

.card__header--dark {
  background: #333;
  color: white;
}

.card__title {
  margin: 0;
  font-size: 1.25rem;
}

.button {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 4px;
}

.button--primary {
  background: #007bff;
  color: white;
}

.button--large {
  padding: 0.75rem 1.5rem;
  font-size: 1.125rem;
}

.button__icon {
  margin-right: 0.5rem;
}

✅ Benefits

• No naming conflicts - Each class is scoped
• Clear structure - You know what belongs where
• Reusable - Blocks work anywhere
• Maintainable - Easy to find and modify styles
• Team-friendly - Everyone follows same convention

🎯 Quick Rules

1. Block names: Describe what it is (.search-form, .user-card)
2. Element names: Describe the part (.search-form__input, .user-card__avatar)
3. Modifier names: Describe the variation (.button--large, .card--featured)
4. No nesting: .block__element__subelement ❌
5. Use semantic names: .card__title ✅ not .card__big-text ❌

BEM makes CSS as organized and maintainable as your JavaScript code!