What are the ways to use css in vue to replace scoped with modules?

This article mainly introduces the method of using css modules instead of scoped in vue. Now I will share it with you and give you a reference.

Previous words

css modules is a popular system for modularizing and combining CSS. vue-loader provides integration with css modules as an alternative to scoped CSS. This article will introduce css modules in detail

Introduction

When I first started using Vue, I advocated and used a lot of scoped technology

<style scoped>
 @media (min-width: 250px) {
  .list-container:hover {
   background: orange;
  }
 }
</style>

This The optional scoped attribute will automatically add a unique attribute (such as data-v-21e5b78) to specify the scope for the CSS within the component. When compiling, .list-container:hover will be compiled into something like .list-container[data-v- 21e5b78]:hover

However, it does not completely avoid conflicts

<span data-v-0467f817 class="errShow">用户名不得为空</span>

Take the above code as an example. After using scoped, it adds a unique attribute 'data-v' to the element. -0467f817', the CSS style is compiled as follows

.errShow[data-v-0467f817] {
  font-size: 12px;
  color: red;
}

However, if the user also defines an errShow class name, it will affect the display of all components defined as the errShow class name

And CSS modules It does it more thoroughly. Instead of adding attributes, it directly changes the class name

<span class="_3ylglHI_7ASkYw5BlOlYIv_0">用户名不得为空</span>

. This greatly reduces the possibility of conflicts. As long as the user does not directly set the style for the span tag, it will basically not affect the component. The display of

Modularity

CSS Modules is neither an official standard nor a browser feature, but a limitation of the CSS class name selector during the build step. A way of domain (implementing a namespace-like method through hash). The class name is dynamically generated, unique, and accurately corresponds to the style of each class in the source file

In fact, CSS Modules is just a way of CSS modularization. Why do we need CSS modularity?

CSS rules are global, and the style rules of any component are valid for the entire page. Therefore, what needs to be solved urgently is the problem of style conflict (pollution). Generally, in order to resolve conflicts, the class name will be written longer to reduce the probability of conflict; a selector of the parent element will be added to limit the scope, etc.

CSS modularization is to solve this problem. Generally, it is divided into three categories

1. Naming convention class

This type of CSS modular solution is mainly used to standardize CSS naming. The most common one is BEM, and of course OOCSS Etc., before the emergence of building tools, most of them were making fuss about CSS naming

2, CSS in JS

Completely abandon CSS and use javascript to write CSS rules. The common ones are styled -components

3. Use JS to manage styles

Use JS to compile native CSS files to make them modular. The most common one is CSS Modules

With the rise of build tools, more and more people are beginning to use the latter two solutions. When writing CSS, they no longer need to worry about style conflicts. You only need to write code in the agreed format

Writing method

The following will introduce how to write CSS modules

Add the module attribute in the style tag. Indicates opening the module mode of CSS-loader

<style module>
.red {color: red;}</style>

Use dynamic class binding: class in the template, and add '$style.' in front of the class name

<template>
 <p :class="$style.red">
  This should be red
 </p>
</template>

If the class name contains Underline, use square bracket syntax

<h4 :class="$style[&#39;header-tit&#39;]">类别推荐</h4>

You can also use array or object syntax

  <p :class="{ [$style.red]: isRed }">
   Am I red?
  </p>
  <p :class="[$style.red, $style.bold]">
   Red and bold
  </p>

More complex object syntax

  <ul 
　　　 :class="{
    [$style.panelBox]:true,
    [$style.transitionByPanelBox]:needTransition
   }"

More complex array syntax

  <li
   :class="[
    $style[&#39;aside-item&#39;],
    {[$style[&#39;aside-item_active&#39;]]:(i === index)}
   ]"

Configuration

css-loader’s default configuration for CSS modules is as follows

{
 modules: true,
 importLoaders: 1,
 localIdentName: '[hash:base64]'
}

You can use the cssModules option of vue-loader to customize the configuration for css-loader

module: {
 rules: [
  {
   test: '\.vue$',
   loader: 'vue-loader',
   options: {
    cssModules: {
     localIdentName: '[path][name]---[local]---[hash:base64:5]',
     camelCase: true
    }
   }
  }
 ]
}

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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