Css

PostCSS相关

Posted by Qz on April 14, 2018

“Yeah It’s on. ”

正文

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Some things you may think about PostCSS

一个后处理器

本身是一个 Node.js 模块，可将 CSS 解析为抽象语法树 (AST)；通过任意数量的“插件”函数传递该 AST；然后将该 AST 转换回字符串

https://segmentfault.com/a/1190000003909268

postcss处理css的方式，主要区分三部分：

  • parser过程：将css字符串解析成可供我们操作的JavaScript对象
  • processor过程：我们应用postcss插件、或是自定义插件，都是在这个过程中，根据postcss提供的API，对parser生成的js对象做相应调整；
  • stringfier过程：将我们处理后的js对象，再转换回为css字符串

https://segmentfault.com/a/1190000015155639

postcss-loader

https://www.npmjs.com/package/postcss-loader

Loader for webpack to process CSS with PostCSS

**Use it after css-loader and style-loader, but before other preprocessor loaders like e.g sass less stylus-loader, if you use any.** 
webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [ 'style-loader', 'postcss-loader' ]
      }
    ]
  }
}

When postcss-loader is used standalone (without css-loader) don’t use @import in your CSS, since this can lead to quite bloated bundles

.postcssrc.js

在vue项目中.postcssrc.js 的默认配置

// https://github.com/michael-ciniawsky/postcss-load-config

module.exports = {
  "plugins": {
    "postcss-import": {},
    "postcss-url": {},
    // to edit target browsers: use "browserslist" field in package.json
    "autoprefixer": {}
  }
}

配置

extract

https://github.com/egoist/rollup-plugin-postcss?tab=readme-ov-file#extract-css

inject

https://github.com/egoist/rollup-plugin-postcss?tab=readme-ov-file#inject

Inject CSS into <head>, it’s always false when extract: true.

插件

postcss-preset-env

https://www.npmjs.com/package/postcss-preset-env

postcss-preset-env vs autoprefixer

PostCSS Preset Env 可以将现代 CSS 转换为大多数浏览器可以理解的内容，并根据目标浏览器或运行时环境确定所需的 polyfill

The browsers option determines which polyfills are required based upon the browsers you are supporting.

PostCSS Preset Env supports any standard browserslist configuration, which can be a .browserslistrc file, a browserslist key in package.json, or browserslist environment variables.

postcss-import

https://www.npmjs.com/package/postcss-import

PostCSS plugin to transform @import rules by inlining content.

postcss-import主要功有是解决@import引入路径问题。使用这个插件，可以让你很轻易的使用本地文件、node_modules或者web_modules的文件。这个插件配合postcss-url让你引入文件变得更轻松。

Notes: This plugin should probably be used as the first plugin of your list. This way, other plugins will work on the AST as if there were only a single file to process, and will probably work as you can expect.

postcss-url

PostCSS plugin to rebase, inline or copy on url().

autoprefixer

现在被 postcss-preset-env 代替了

autoprefixer has complex logic to fix CSS Grid in IE and older Edge.

autoprefixer在IE和旧版Edge中有复杂的逻辑来修复CSS Grid。

PostCSS plugin to parse CSS and add vendor prefixes to CSS rules using values from Can I Use. It is recommended by Google and used in Twitter and Taobao.

Because Autoprefixer is a postprocessor for CSS(后处理器), you can also use it with preprocessors such as Sass, Stylus or LESS.

Browsers

Autoprefixer uses Browserslist, so you can specify the browsers you want to target in your project by queries like last 2 versions or > 5%.

The best way to provide browsers is .browserslistrc config or package.json with browserslist key. Put it in your project root.

We recommend to avoid Autoprefixer option and use .browserslistrc config or package.json. In this case browsers will be shared with other tools like babel-preset-env or Stylelint.

postcss-cssnext

postcss-cssnext其实就是cssnext。该插件可以让我们使用CSS未来的特性，其会对这些特性做相关的兼容性处理。其包含的特性主要有：

enter description here

cssnano

https://www.npmjs.com/package/cssnano A modular minifier, built on top of the PostCSS ecosystem.

cssnano主要用来压缩和清理CSS代码。在Webpack中，cssnano和css-loader捆绑在一起，所以不需要自己加载它。不过你也可以使用postcss-loader显式的使用cssnano

@svg square {
	@rect {
		fill: var(--color, black);
		width: 100%;
		height: 100%;
	}
}

#example {
	background: white svg(square param(--color #00b1ff));
}

转为

#example {
	background: white url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg'%3E%3Crect fill='%2300b1ff' width='100%25' height='100%25'/%3E%3C/svg%3E");
}

postcss-mpvue-wxss

专门为 wxss 格式化处理的的一个 postcss 插件，特别是在做 css 转 wxss 的时候好用到爆。

实现的功能

  • 清理 wxss 不支持的选择器。
  • 清理 wxss 不支持的注释。
  • 转换 rem 单位到 rpx。
  • 转换 Web 的标签选择器到小程序的 class 选择器。
  • style scoped（postcss插件部分）。

postcss-px2rem

This is a postcss plugin of px2rem.

“autoprefixer”: {remUnit: 75}

postcss-pxtorem-exclude

https://www.npmjs.com/package/postcss-pxtorem-exclude

A plugin for PostCSS that generates rem units from pixel units.

A message about ignoring properties

Currently, the easiest way to have a single property ignored is to use a capital in the pixel unit declaration.

// `px` is converted to `rem`
.convert {
    font-size: 16px; // converted to 1rem
}
 
// `Px` or `PX` is ignored by `postcss-pxtorem-exclude` but still accepted by browsers
.ignore {
    border: 1Px solid; // ignored
    border-width: 2PX; // ignored
}

postcss-custom-properties

https://github.com/postcss/postcss-custom-properties

const postcss = require('postcss');
const postcssCustomProperties = require('postcss-custom-properties');

postcss([
  postcssCustomProperties(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);

postcssCustomProperties({
  preserve: false
});

The preserve option determines whether Custom Properties and properties using custom properties should be preserved in their original form. By default, both of these are preserved.

该preserve选项确定是否应以原始形式保留使用自定义属性的自定义属性和属性。默认情况下，这两个都被保留。

举个例子

:root {
  --color: red;
}

h1 {
  color: var(--color);
}

/* becomes */

h1 {
  color: red;
}

postcss-sprite

https://www.npmjs.com/package/postcss-sprites

https://github.com/2createStudio/postcss-sprites

PostCSS plugin that generates spritesheets from your stylesheets.

/* Input */
.comment { background: url(images/sprite/ico-comment.png) no-repeat 0 0; }
.bubble { background: url(images/sprite/ico-bubble.png) no-repeat 0 0; }
 
/* ---------------- */
 
/* Output */
.comment { background-image: url(images/sprite.png); background-position: 0 0; }
.bubble { background-image: url(images/sprite.png); background-position: 0 -50px; }

Share your code. npm Orgs help your team discover, share, and reuse code. Create a free org » postcss-spritespublic

PostCSS plugin that generates spritesheets from your stylesheets.

/* Input */
.comment { background: url(images/sprite/ico-comment.png) no-repeat 0 0; }
.bubble { background: url(images/sprite/ico-bubble.png) no-repeat 0 0; }
 
/* ---------------- */
 
/* Output */
.comment { background-image: url(images/sprite.png); background-position: 0 0; }
.bubble { background-image: url(images/sprite.png); background-position: 0 -50px; }

         {
                                loader: 'postcss-loader',
                                options: {
                                    ident: 'postcss',
                                    plugins: [
                                        // CSS 雪碧图
                                        require('postcss-sprites')({
                                            spritePath: 'dist/assets/imgs/sprites',
                                            retina: true
                                        }),
                                        require('postcss-cssnext')()
                                    ]
                                }
                            }

适配retina屏幕(2倍大小图片等) retina: true

###

postcss-assets

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