README

PostCSS Custom Selector

PostCSS 实现 W3C CSS Extensions(Custom Selectors) 的插件。

安装(暂未发布)

$ npm install postcss-custom-selector

快速开始

// dependencies
var fs = require('fs')
var postcss = require('postcss')
var selector = require('postcss-custom-selector')

// css to be processed
var css = fs.readFileSync('input.css', 'utf8')

// process css using postcss-custom-selector
var output = postcss()
  .use(selector())
  .process(css)
  .css
  
console.log('\n\n ====>Output CSS:\n',output)

或者：

var output = postcss(selector())
  .process(css)
  .css

input.css：

@custom-selector --heading h1, h2, h3, h4, h5, h6;

article --heading + p{ 
  margin-top: 0;
}

你将得到：

article h1 + p, article h2 + p, article h3 + p, article h4 + p, article h5 + p, article h6 + p{
  margin-top: 0;
}

CSS 语法

A custom selector is defined with the @custom-selector rule:

@custom-selector = @custom-selector <extension-name> <selector>;

This defines a custom selector which is written as a pseudo-class with the given <extension-name>, and represents a :matches() selector using the provided <selector> as its argument.

For example, if an author wanted to easily refer to all heading elements in their HTML document, they could create an alias:

@custom-selector :--heading h1, h2, h3, h4, h5, h6;

:--heading { /* styles for all headings */ }
:--heading + p { /* more styles */ }
/* etc */

如何使用

伪元素/伪类

你可以使用

: 自定义一个伪类。
::自定义一个伪元素。

例如，模拟一个 :any-link 选择器：

input.css:

@custom-selector :--any-link :link, :visited;

a:--any-link {
  color: blue;
}

output:

a:link, a:visited {
  color: blue;
}

多个选择器

@custom-selector 类似 CSS :matches() 选择器，但是目前不支持在同一个选择器中调用多个自定义选择器，例如：

@custom-selector --heading h1, h2, h3, h4, h5, h6;
@custom-selector :--any-link :link, :visited;

.demo --heading, a:--any-link { 
  font-size: 32px;
}

将会输出错误的 CSS 代码。

Grunt

grunt.initConfig({
  postcss: {
    options: {
      processors: [require('postcss-custom-selector').postcss]
    },
    dist: {
      src: 'css/*.css'
    }
  }
});

grunt.loadNpmTasks('grunt-postcss');

Gulp

var gulp = require('gulp');
var postcss = require('gulp-postcss');

gulp.task('css', function() {
  return gulp.src('./src/*.css')
    .pipe(postcss([require('postcss-custom-selector')]))
    .pipe(gulp.dest('./dest'));
});

选项

extensions (默认: {})

该选项允许你自定义一个对象来设置 <extension-name>（选择器别名）和 <selector>，这些定义将覆盖 CSS 中相同别名的 @custom-selector。

var options = {
  extensions: {
    ':--any' : 'section, article, aside, nav'
  }
}

var output = postcss(selector(options))
  .process(css)
  .css;

input.css

@custom-selector :--any .foo, .bar; /* 不会生效 */
:--any h1 {
  margin-top: 16px;
}