bem_conventions_css.md

BEM Naming Convention

BEM stands for Block, Element, Modifier and is a methodology used to create reusable components in CSS by clearly defining and separating the roles of different class names.

Overview of BEM Components

• Block: The outermost parent component that acts as a standalone entity. For example, .button.
• Element: A part of the block that has no standalone meaning and is semantically tied to its block. For example, .button__text.
• Modifier: A flag on a block or element that changes its appearance or behavior. For example, .button--large.

BEM Example: Stick-Man (CSS)

BEM organizes CSS by using a structured class naming convention that enhances readability and maintainability. Here is an example using a simple stick-man illustration:

• Block: .stick-man - Represents the whole stick-man.
• Elements:
  • .stick-man__head - The head of the stick-man.
  • .stick-man__arms - The arms.
  • .stick-man__feet - The feet.
• Modifiers:
  • .stick-man--blue - A blue version of the stick-man.
  • .stick-man__head--small - A small head variation.

HTML Structure

<div class="stick-man stick-man--blue">
  <div class="stick-man__head stick-man__head--small"></div>
  <div class="stick-man__arms"></div>
  <div class="stick-man__feet"></div>
</div>

BEM Example: Button (CSS)

Suppose you are creating a user interface with a button that has different sizes and colors. Using BEM, the structure is defined as follows:

• Block: .button - The base class for all buttons.
• Modifiers:
  • .button--large - Modifies the button to be larger.
  • .button--success - Modifies the button's color to indicate success (green).
• Element:
  • .button__text - Targets the text within the button.

<button class="button button--large button--success">
  <span class="button__text">Submit</span>
</button>

React Example: Product List

Overview

Implementing BEM in React with a ProductList as the block and ProductListItem as elements within that block.

ProductList Component (Block)

This component serves as a container for product items.

// ProductList.jsx
import React from 'react';
import ProductListItem from './ProductListItem';

const products = [
  { id: 1, name: 'Apple', price: '$1' },
  { id: 2, name: 'Banana', price: '$2' },
  { id: 3, name: 'Cherry', price: '$3' },
];

function ProductList() {
  return (
    <div className="product-list">
      {products.map(product => (
        <ProductListItem key={product.id} product={product} />
      ))}
    </div>
  );
}

export default ProductList;

ProductListItem Component (Element)

Each item in the product list is an element of the ProductList block.

// ProductListItem.jsx
import React from 'react';

function ProductListItem({ product }) {
  return (
    <div className="product-list__item">
      <h2 className="product-list__item-name">{product.name}</h2>
      <p className="product-list__item-price">{product.price}</p>
    </div>
  );
}

export default ProductListItem;

Explanation:

• Block: .product-list - Represents the entire list of products.
• Element: .product-list__item, .product-list__item-name, and .product-list__item-price - These elements are part of the ProductList and help in organizing components in a modular and reusable way.