Briefly analyze the 5 design patterns in CSS and talk about the role of CSS directory code in the vue project

This article will talk about the 5 design patterns in CSS, and introduce the code functions in the CSS style directory in the vue3 project. I hope it will be helpful to everyone!

After working for several years, I found that the following problems often exist in projects:

• 1. Unreasonable module splitting
• 2. The naming of variables and functions is unclear
• 3. There is a lack of comments or a bunch of unclear descriptions
• 4. Duplicate codes are everywhere

Because of these bad programming habits, projects have become increasingly difficult to maintain and program performance has become lower and lower, greatly reducing daily work efficiency and increasing the company's development costs.

The following will take the CSS architecture in the Vue3 project as an entry point to improve our programming capabilities and project architecture capabilities by reducing the redundancy of CSS code and enhancing the maintainability and scalability of CSS code.

Technical reserves:

• Sass（https://www.sass.hk/docs/）
• Vue3（https://v3.cn.vuejs .org/)
  

CSS design patterns

Before learning the CSS architecture, let’s take a brief look at the five common CSS design patterns. These design patterns are Our CSS architecture provides certain development ideas.

1.OOCSS mode

OOCSS (Object-Oriented CSS) literally means object-oriented CSS, and it has the following specifications during development

• Reduce dependence on HTML structure

# bad
# 1.匹配效率低，影响css性能
# 2.和html耦合度高，维护性和扩展性低
.container-list ul li a {}

<div class="container-list">
  <ul>
    <li>
      <a>...</a>
    </li>
  </ul>
</div>


# good
.container-list .list-item {}

<div class="container-list">
  <ul>
    <li>
      <a class="list-item">...</a>
    </li>
  </ul>
</div>

• Increase the reusability of styles

.label {
  # 公共代码
}
.label-danger {
  # 特定代码
}
.label-info {
  # 特定代码
}
<div>
  <p class="label label-danger"></p>
  <p class="label label-info"></p>
</div>

2.BEM mode

BEM is an advanced version of OOCSS, a layered system that divides our website into three layers. These three layers correspond to the abbreviations of the three English words BEM: block, element, Modifier is divided into block layer, element layer and modifier layer.

To embody BEM into code, we need to follow three principles:

• Use __ two underscores to separate the block name from the element name
• Use - -Two dashes separate the element name and its modifiers
• All styles are a class and cannot be nested.

<div class="menu">
  <div class="menu__tab menu__tab--style1">tab1</div>
  <div class="menu__tab menu__tab--style1">tab2</div>
</div>

However, due to the two underscores __ and two dashes - it is not so smooth in actual development and affects development efficiency. However, if the CSS naming convention must be strictly controlled, this is undoubtedly a problem. Good choice. And when writing CSS, we can encapsulate a BEM.scss file through Sass’s mixed instructions to reduce the input of class names and enhance the CSS structure

3. SMACSS mode

BEM's simple three-layer classification method has no problem in dealing with small and medium-sized websites, but it may be more difficult to deal with the styles of complex websites. We need to find a better way.

SMACSS (Scalable and Modular Architecture for CSS) is about writing modular, structured and extensible CSS. It divides the CSS in the project into five categories

• Base: Default attribute style reset, the well-known library is normalize.css
• Layout: Layout style
• Modules : Reusable module styles, such as some list displays
• State: State styles, such as gray or highlighted buttons
• Theme: Skin styles, such as some websites with skin changes Function
  

4.ITCSS mode

ITCSS (Inverted Triangle Cascading Style Sheets) can be translated as"Inverted Triangle CSS", which divides the styles in our project into seven layers based on the concept of layering

• Settings: Project style variables, such as theme color, font, etc.
• Tools: Tool class Style, such as defining a function to indicate the presence of ellipses when too many words are used
• Generic: reset and/or standardize styles, box size definitions, etc., corresponding to normalize.css
• Base: Reset Set the default value of browser element attributes
• Objects: Maintain OOCSS styles
• Components: Public component styles
• Trumps: Make the style weight the highest, utility and auxiliary classes , can overwrite any previous content in the triangle, the only important! place
  

5.ACSS mode

ACSS (Atomic CSS) is translated as "Atomic CSS" is a CSS architecture method that favors small and single-purpose classes and is named after visual effects. It is a WYSIWYG language that does not emphasize logic but focuses more on performance. The background of its emergence is the arrival of the era of front-end componentization. The CSS of each component can be independent of each other and do not affect each other. Therefore, such code appears

<button class="bg-blue-500 hover:bg-blue-700 text-white font-bold py-2 px-4 rounded">按钮</button>

The more mature ACSS libraries currently on the market include: Tailwind CSS and Windi CSS

Advantages of ACSS

• CSS文件停止增长：使用传统方法，每次添加新功能时，您的 CSS 文件都会变大。使用实用程序，一切都是可重用的，因此您很少需要编写新的 CSS，一套样式全局通用。
• 不再浪费精力命名，不再添加愚蠢的类名：例如 sidebar-inner-wrapper 只是为了能够设置样式，也不再为真正只是一个 flex 容器的东西的完美抽象名称而苦恼。
• 灵活，易读：CSS 是全球性的，当你做出改变时，你永远不知道你破坏了什么。HTML 中的类是本地的，因此可以 插拔式改变样式 而不必担心其他问题，CSS 样式很多缩写更加符合大脑的记忆。
• 永远不用担心命名冲突，永远不用担心样式覆盖。

ACSS的缺点

• 会增加HTML 的体积
• 破坏了CSS命名的语义化
• 熟悉命名 ACSS 命名会有一定成本

综上，我们可以看出ACSS 劣处是非常小的，而好处有非常大，没有理由在项目中不适用。下面我们通过使用BEM、ITCSS和ACSS模式打造一套CSS架构方案。

项目搭建

创建vue3项目和安装依赖

• 1.创建vue3项目
• 2.安装：npm i sass@1.26.5 sass-loader@8.0.2 --save
  

CSS目录结构展示与说明

src
  style
    acss         # 存放boder、margin、padding等基于acss模式的代码
    base         # 存放元素(input、p、h1等)的重置样式
    settings     # 存放项目统一规范的文本颜色、边框颜色等变量
    theme        # 存放项目特定主题下的元素样式
    tools        # 存放封装好的mixin(混合指令)和function(函数)样式
    global.scss  # 需要项目全局引用的CSS
    index.scss   # 需要Vue文件引用的CSS

1.关于mixin(混合指令)和function(函数)的区别

• 函数是有计算逻辑，返回计算的结果，不输出css块
• mixin主要是根据计算结果输出css块

/* mixin */
@mixin center-translate($direction: both) {
  position: absolute;
  @if $direction == both {
    top: 50%;
    left: 50%;
    transform: translate3d(-50%, -50%, 0);
  } @else if $direction == horizontal {
    left: 50%;
    transform: translate3d(-50%, 0, 0);
  } @else if $direction == vertical {
    top: 50%;
    transform: translate3d(0, -50%, 0);
  }
}

/* function */
@function am($module, $trait: false) {
  @if $trait==false {
    @return '[am-' + $module + ']';
  } @else {
    @return '[am-' + $module + '~="' + $trait + '"]';
  }
}

2.关于style/global.scss和style/index.scss

• global.scss中导入的代码不仅在Vue文件中使用，而且在style中scss定义文件里也会被引用到

# style/global.scss
@import "./settings/var.scss";

# style/settings/var.scss
$background-color-primary: #F1F1F1;
$background-color-secondary: $color-white;

# style/acss/color.scss
@each $style in (primary $background-color-primary, secondary $background-color-secondary) {
  [bg-#{nth($style, 1)}] {
    background-color: #{nth($style, 2)};
  }
}

• 全局引入style/global.scss

// 根目录下：vue.config.js
module.exports = {
  css: {
    loaderOptions: {
      scss: {
        // @/ 是 src/ 的别名
        // 注意：在 sass-loader v8 中，这个选项名是 "prependData"
        prependData: `@import "@/style/global.scss";`
      },
    }
  }
}

• style/index.scss定义的代码只是不被style中其他css文件引用到而已，其他的都和global.scss一致
• 引入style/index.scss

// src/main.js
import { createApp } from 'vue'
import App from './App.vue'
import router from './router'
import './style/index.scss'

createApp(App).use(router).mount('#app')

下面简单分析和演示下各个style目录中的代码作用。

1.acss

该目录主要是定义一些简单的border、color、font-size、margin和padding等代码

/* style/acss/border.scss */
@for $i from 1 through 100 {
  [radius#{$i}] { 
    border-radius: #{$i}Px;
    overflow: hidden;
  }
}
[circle] {
  border-radius: 50%;
}

/* style/acss/font-size.scss */
@for $i from 12 through 30 {
  [fz#{$i}] { 
    font-size: #{$i}px;
  }
}

使用acss代码

<div class="container">
  <div class="item" radius20>border-radius: 20px;</div>
</div>
<div class="container">
  <div class="item" circle>border-radius: 50%;</div>
</div>
<div class="container">
  <div class="item" fz30>font-size: 30px;</div>
</div>

2.base

该目录主要是重置项目中一些元素的默认样式，比如input、hn、p、a等元素

/* style/base/form.scss */
input {
  padding: 0;
  outline: none;
  border: none;
}

/* style/base/link.scss */
a {
  color: #ccc;
  text-decoration: none;
}

3.settings

该目录是定义全局的、项目统一规范的文本颜色、边框颜色等变量

/* style/settings/var.scss */
/* 主题色调 */
$color-primary: #FF5777;
$color-white: #FFFFFF;

/* 文本色调 */
$color-text-primary: green;
$color-text-secondary: #FF4533;
$color-text-tertiary: $color-white;
$color-text-quaternary: $color-primary;

/* 盒子边框色调 */
$border-color-base: #E5E5E5;

/* 盒子背景色色调 */
$background-color-primary: #F1F1F1;
$background-color-secondary: $color-white;
$background-color-tertiary: $color-primary;


/* 盒子默认边框 */
$border-width-base: 1Px !default;
$border-style-base: solid !default;
$border-base: $border-width-base $border-style-base $border-color-base !default;

4.theme

该目录定义项目各个主题下相关模块的样式

/* style/theme/default.scss */
[data-theme='default'] .header {
  background: #FF5777;
}
[data-theme='default'] .footer {
  color: #FF5777;
  border: 2px solid #FF5777;;
}

/* style/theme/cool.scss */
[data-theme='cool'] .header {
  background: #409EFF;
}
[data-theme='cool'] .footer {
  color: #409EFF;
  border: 2px solid #409EFF;;
}

我们通过添加html元素上的data-theme属性和值，即可达到项目主题的变换

<!-- Theme.vue -->
<template>
  <div class="theme">
    <div class="header"></div>
    <div class="theme__set">
      <div class="set set--default" @click="changeTheme(&#39;default&#39;)"></div>
      <div class="set set--cool" @click="changeTheme(&#39;cool&#39;)"></div>
    </div>
    <div class="footer"></div>
  </div>
</template>

<script>
export default {
  name: "Theme",
  setup() {
    const changeTheme = (theme = &#39;default&#39;) => {
      window.document.documentElement.setAttribute("data-theme", theme);
    }
    return {
      changeTheme
    }
  }
}
</script>


<!-- Other.vue -->
<template>
  <div class="about">
    <div class="header"></div>
    <div class="about-title">This is an about page title</div>
    <div class="about-content">This is an about page content</div>
    <div class="footer"></div>
  </div>
</template>

5.tools

该目录是定义一些全局的公共mixin和function，目前这块内容比较完善就是SassMagic，感兴趣的可以点进来看一下。下面简单看一下BEM模式的应用

$elementSeparator: '__';
$modifierSeparator: '--';

// 判断`$selector`中是否包含BEM中Modify
@function containsModifier($selector) {
  $selector: selectorToString($selector);
  @if str-index($selector, $modifierSeparator) {
    @return true;
  } @else {
    @return false;
  }
}

// 将`$selector`转换成String
@function selectorToString($selector) {
  $selector: inspect($selector); //cast to string
  $selector: str-slice($selector, 2, -2); //remove brackets
  @return $selector;
}

// @param  {String}  $selector
@function getBlock($selector) {
  $selector: selectorToString($selector);
  $modifierStart: str-index($selector, $modifierSeparator) - 1;
  @return str-slice($selector, 0, $modifierStart);
}

@mixin b($block) {
  .#{$block} {
    @content;
  }
}

@mixin e($element) {
  $selector: &;
  @if containsModifier($selector) {
    $block: getBlock($selector);
    @at-root {
      #{$selector} {
        #{$block + $elementSeparator + $element} {
          @content;
        }
      }
    }
  } @else {
    @at-root {
      #{$selector + $elementSeparator + $element} {
        @content;
      }
    }
  }
}

@mixin m($modifier) {
  @at-root {
    #{&}#{$modifierSeparator + $modifier} {
      @content;
    }
  }
}

// @param {string} $block - BEM中的Block
// <div class="block">
//   <div class="block__header">
//     <div class="block__header--css"></div>
//   </div>
// </div>

//  @include b(block) {
//    background: red;
//    @include e(header){
//       font-size: 14px;
//       @include m(css) {
//         font-size: 18px;
//      }
//   };
// }

// 编译后
// .block {
//   background: red;
// }
// .block__header {
//   font-size: 14px;
// }
// .block__header--css {
//   font-size: 18px;
// }

尾声

暂时先讲这么多，更多内容可以关注下这个仓库vue3-css-architecture，会持续更新完善，补充更多的mixin、function，以及在项目中的应用。

（学习视频分享：css视频教程）

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