# CSS design patterns

These examples are for documenting CSS-specific design patterns like BEM, OOCSS and SMACSS.

These examples are NOT for documenting CSS frameworks like Bootstrap or Foundation.


BEM stands for Blocks, Elements and Modifiers. It's a methodology initially conceived by Russian tech company Yandex, but which gained quite some traction among American & Western-European web developers as well.

As the same implies, BEM metholology is all about componentization of your HTML and CSS code into three types of components:

  • **Blocks:** standalone entities that are meaningful on their own Examples are `header`, `container`, `menu`, `checkbox` & `textbox`
  • **Elements:** Part of blocks that have no standalone meaning and are semantically tied to their blocks. Examples are `menu item`, `list item`, `checkbox caption` & `header title`
  • **Modifiers:** Flags on a block or element, used to change appearance or behavior Examples are `disabled`, `highlighted`, `checked`, `fixed`, `size big` & `color yellow`
  • The goal of BEM is to keep optimize the readability, maintainability and flexibility of your CSS code. The way to achieve this, is to apply the following rules.

    • Block styles are never dependent on other elements on a page
    • Blocks should have a simple, short name and avoid _ or - characters
    • When styling elements, use selectors of format blockname__elementname
    • When styling modifiers, use selectors of format blockname--modifiername and blockname__elementname--modifiername
    • Elements or blocks that have modifiers should inherit everything from the block or element it is modifying except the properties the modifier is supposed to modify

    # Code example

    If you apply BEM to your form elements, your CSS selectors should look something like this:

    .form { }                       // Block
    .form--theme-xmas { }           // Block + modifier
    .form--simple { }               // Block + modifier
    .form__input { }                // Block > element
    .form__submit { }               // Block > element
    .form__submit--disabled { }     // Block > element + modifier

    The corresponding HTML should look something like this:

    <form class="form form--theme-xmas form--simple">
      <input class="form__input" type="text" />
      <input class="form__submit form__submit--disabled" type="submit" />

    # Remarks

    These examples are for documenting CSS-specific methodologies / design patterns.

    These methodologies include but are not exclusive to the following:

    These examples are NOT for documenting CSS frameworks like Bootstrap or Foundation. While you may include examples of how to apply one or more CSS methodology / design pattern with a CSS framework, those examples are to focus on the methodologies / design patterns with that particular framework and on the use of the framework itself.