search
HomeWeb Front-endCSS TutorialWhat is the BEM naming convention in CSS?
What is the BEM naming convention in CSS?Sep 10, 2018 pm 04:00 PM
cssNaming conventions

This chapter brings you what is the BEM naming convention in CSS? , has certain reference value, friends in need can refer to it, I hope it will be helpful to you.

1 What is the BEM naming convention

Bem is the abbreviation for block, element, and modifier. It is a front-end CSS naming methodology proposed by the Yandex team.

- Dash: Used only as a hyphen to represent a connection mark between multiple words of a block or a sub-element.
__Double underline: Double underline is used to connect blocks and sub-elements of the block
_ Single underscore: A single underscore is used to describe a state of a block or a sub-element of a block

BEM is a simple and very useful naming convention. Make your front-end code easier to read and understand, easier to collaborate with, easier to control, more robust and unambiguous, and more rigorous.

1. BEM naming pattern

The BEM naming convention pattern is:

.block {}
.block__element {}
.block--modifier {}

Each block (block) name should have a namespace (prefix)
Block represents a higher level abstraction or component.
block__element represents the descendants of .block and is used to form a complete .block as a whole.
block--modifier represents different states or different versions of .block

Use two hyphens and underscores instead of one so that your own blocks can be delimited with a single hyphen . Such as:

.sub-block__element {}
.sub-block--modifier {}

2. The benefits of BEM nomenclature

The key to BEM is that you can get more descriptions and a clearer structure, and you can know the meaning of a certain mark from its name. Therefore, by looking at the class attribute in the HTML code, you can know the relationship between elements.

Conventional nomenclature example:

<div class="article">
    <div class="body">
        <button class="button-primary"></button>
        <button class="button-success"></button>
    </div>
</div>

This way of writing can understand the meaning of each element from the DOM structure and class naming, but it cannot clarify its true hierarchical relationship. When defining CSS, you must also rely on hierarchical selectors to limit the constraint scope to avoid cross-component style pollution.

Examples using the BEM naming method:

<div class="article">
    <div class="article__body">
        <div class="tag"></div>
        <button class="article__button--primary"></button>
        <button class="article__button--success"></button>
    </div>
</div>

Through the BEM naming method, the module hierarchical relationship is simple and clear, and there is no need to make too many hierarchical choices when writing css.

2. How to use BEM nomenclature

1. When should you use BEM format

The trick to using BEM is , you need to know when and what should be written in BEM format. Not every place should use BEM naming. The BEM format should be used when explicit module relationships are required. For example, if there is just a single public style, there is no point in using the BEM format:

.hide {    display: none !important;}

2. Using the BEM format in the CSS preprocessor

One disadvantage of BEM is the naming method It is long, ugly and poorly written. Compared with the convenience brought by the BEM format, we should look at it objectively. Moreover, CSS is generally written using preprocessor languages ​​such as LESS/SASS, and it is much simpler to write using its language features.

Take LESS as an example:

.article {
    max-width: 1200px;
    &__body {
        padding: 20px;
    }
    &__button {
        padding: 5px 8px;
        &--primary {background: blue;}
        &--success {background: green;}
    }
}

3 Using BEM format in components of popular frameworks
In the currently popular front-end frameworks such as Vue.js / React / `Angular, there are compilation implementations of CSS component-level scope. The basic principle is to use the CSS attribute selector feature to generate different attribute selectors for different components. .
When you choose this local scope approach, the BEM format may seem less important in smaller components. However, for public and global module style definitions, it is still recommended to use the BEM format.
In addition, for public components released to the outside world, generally for the sake of style customization, this local scope method is not used to define component styles. This is where using the BEM format will also come in handy.

4 Avoid the .block__el1__el2 format
In deeply nested DOM
structure, overly long style name definitions should be avoided.
The final level should not exceed level 4, otherwise it will increase the difficulty of reading comprehension

3. Summary

One of the most difficult parts of BEM It is clear where the scope starts and ends, and when to use it or not to use it. As you accumulate experience with continuous use, you will slowly know how to use it, and these problems will no longer be a problem. There is no good or bad technology, only the right one is best.

Recommended writing and style

//常规写法:
.xxx{}
.xxx__item{}
.xxx__item_current{}

// 嵌套写法
.xxx__item_current .mod-xxx__link{}

推荐:
.xxx{}
.xxx__item{}
.xxx__item_hightlight{}
.xxx__product-name{}
.xxx__link{}
.xxx__ming-zi-ke-yi-hen-chang{}

// 嵌套写法
.xxx__item_current{
    .xxx__link{}
}

//对应的HTML结构如下:

<ul class="xxx">

	<li class="xxx__item">第一项

		<div class="xxx__product-name">我是名称</div>

		<span class="xxx__ming-zi-ke-yi-hen-chang">看类名</span>

		<a href="#" class="xxx__link">我是link</a>

	</li>

	<li class="xxx__item xxx__item_current">第二项 且 当前选择项

		<div class="xxx__product-name">我是名称</div>

		<a href="#" class="xxx__item-link">我是link</a>

	</li>

	<li class="xxx__item xxx__item_hightlight">第三项 且 特殊高亮

		<div class="xxx__product-name">我是名称</div>

		<a href="#" class="xxx__item-link">我是link</a>

	</li>
</ul>






##

The above is the detailed content of What is the BEM naming convention in CSS?. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
如何优化Java代码的可维护性:经验与建议如何优化Java代码的可维护性:经验与建议Nov 22, 2023 pm 05:18 PM

如何优化Java代码的可维护性:经验与建议在软件开发过程中,编写具有良好可维护性的代码是至关重要的。可维护性意味着代码能够被轻松理解、修改和扩展,而不会引发意外的问题或额外的工作量。对于Java开发者来说,如何优化代码的可维护性是一个重要课题。本文将分享一些经验和建议,帮助Java开发者提升其代码的可维护性。遵循规范的命名规则规范的命名规则能够使代码更易读,

PHP中的命名规范:如何使用PSR标准命名类、方法和变量PHP中的命名规范:如何使用PSR标准命名类、方法和变量Jul 30, 2023 am 11:17 AM

PHP中的命名规范:如何使用PSR标准命名类、方法和变量在PHP开发中,命名规范是一项非常重要的细节,它直接影响代码的可读性和可维护性。PSR(PHPStandardRecommendations)是PHP开发社区共同确定的一系列代码规范标准,包括了一些针对命名的具体要求。本文将介绍如何使用PSR标准规范命名PHP类、方法和变量,并提供代码示例作为参考。

css怎么设置i不是斜体css怎么设置i不是斜体Apr 20, 2022 am 10:36 AM

在css中,可以利用“font-style”属性设置i元素不是斜体样式,该属性用于指定文本的字体样式,当属性值设置为“normal”时,会显示元素的标准字体样式,语法为“i元素{font-style:normal}”。

PHP方法的命名规范与最佳实践PHP方法的命名规范与最佳实践Feb 29, 2024 pm 01:51 PM

PHP方法的命名规范与最佳实践作为一种流行的服务器端脚本语言,PHP被广泛用于开发网站和Web应用程序。在PHP开发中,方法(函数)是非常重要的一部分,良好的命名规范和最佳实践能够提高代码的可读性、可维护性和可扩展性。本文将分享一些关于PHP方法命名的规范和最佳实践,同时提供具体的代码示例。方法命名规范1.使用有意义且描述性的名称方法的名称应当准确地描述方

常见的Python变量命名方法和技巧常见的Python变量命名方法和技巧Jan 20, 2024 am 09:17 AM

Python中常用的变量命名方法和技巧在编程中,良好的变量命名是非常重要的。一个好的变量名可以使代码更易读、易懂,提高代码的可维护性和可扩展性。而不好的变量命名则会使代码难以理解和修改。本文将介绍Python中常用的变量命名方法和技巧,并提供具体的代码示例。使用有意义的变量名一个好的变量名应该能够清晰地表达出变量的含义,使其他人在阅读代码时能够轻松理解其用途

css怎么去除a标签鼠标样式css怎么去除a标签鼠标样式Apr 20, 2022 am 11:07 AM

在css中,可用cursor属性去除a标签的鼠标样式,该属性用于定义鼠标指针在一个元素边界范围内所用的鼠标样式,属性值设置为none时,会去除元素的鼠标样式,设置为default时,显示默认箭头样式,语法为“a{cursor:none}”。

C++ 函数命名:匈牙利表示法与命名规范的比较C++ 函数命名:匈牙利表示法与命名规范的比较May 04, 2024 am 08:18 AM

C++函数命名惯例对比:匈牙利表示法和命名规范。匈牙利表示法通过变量名前缀表示类型,增强可读性但冗长;命名规范使用更简洁的名称,提高可读性。匈牙利表示法强制执行类型检查,提高维护性但可能混乱;命名规范更灵活。匈牙利表示法具有更好的可重用性,而命名规范较差。

PHP函数的命名规范及规则PHP函数的命名规范及规则May 19, 2023 am 08:14 AM

PHP作为一种非常流行的脚本语言,有着强大的函数库支持,其函数的命名规范和规则对于开发效率和代码可读性都有着重要的影响。本文将介绍PHP函数的命名规范及规则。一、命名风格在PHP中,函数名需要严格符合命名规范和规则,规范主要包括两个方面:命名风格和命名规则。1.下划线命名法下划线命名法是PHP函数命名最常用的方式,也是官方推荐的一种方式。遵循这种方式的函数名

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

mPDF

mPDF

mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),