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1# CSS Has Pseudo [<img src="http://jonathantneal.github.io/js-logo.svg" alt="" width="90" height="90" align="right">][CSS Has Pseudo]
2
3[![NPM Version][npm-img]][npm-url]
4[![Build Status][cli-img]][cli-url]
5[![Support Chat][git-img]][git-url]
6
7[CSS Has Pseudo] lets you style elements relative to other elements in CSS,
8following the [Selectors Level 4] specification.
9
10```css
11a:has(> img) {
12 /* style links that contain an image */
13}
14
15h1:has(+ p) {
16 /* style level 1 headings that are followed by a paragraph */
17}
18
19section:not(:has(h1, h2, h3, h4, h5, h6)) {
20 /* style sections that don’t contain any heading elements */
21}
22
23body:has(:focus) {
24 /* style the body if it contains a focused element */
25}
26```
27
28## Usage
29
30From the command line, transform CSS files that use `:has` selectors:
31
32```bash
33npx css-has-pseudo SOURCE.css TRANSFORMED.css
34```
35
36Next, use your transformed CSS with this script:
37
38```html
39<link rel="stylesheet" href="TRANSFORMED.css">
40<script src="https://unpkg.com/css-has-pseudo/browser"></script>
41<script>cssHasPseudo(document)</script>
42```
43
44That’s it. The script is 765 bytes and works in all browsers, including
45Internet Explorer 11. With a [Mutation Observer polyfill], the script will work
46down to Internet Explorer 9.
47
48## How it works
49
50The [PostCSS plugin](README-POSTCSS.md) clones rules containing `:has`,
51replacing them with an alternative `[:has]` selector.
52
53```css
54body:has(:focus) {
55 background-color: yellow;
56}
57
58section:not(:has(h1, h2, h3, h4, h5, h6)) {
59 background-color: gray;
60}
61
62/* becomes */
63
64body[\:has\(\:focus\)] {
65 background-color: yellow;
66}
67
68body:has(:focus) {
69 background-color: yellow;
70}
71
72section[\:not-has\(h1\,\%20h2\,\%20h3\,\%20h4\,\%20h5\,\%20h6\)] {
73 background-color: gray;
74}
75
76section:not(:has(h1, h2, h3, h4, h5, h6)) {
77 background-color: gray;
78}
79```
80
81Next, the [JavaScript library](README-BROWSER.md) adds a `[:has]` attribute to
82elements otherwise matching `:has` natively.
83
84```html
85<body :has(:focus)>
86 <input value="This element is focused">
87</body>
88```
89
90[cli-img]: https://img.shields.io/travis/csstools/css-has-pseudo/master.svg
91[cli-url]: https://travis-ci.org/csstools/css-has-pseudo
92[git-img]: https://img.shields.io/badge/support-chat-blue.svg
93[git-url]: https://gitter.im/postcss/postcss
94[npm-img]: https://img.shields.io/npm/v/css-has-pseudo.svg
95[npm-url]: https://www.npmjs.com/package/css-has-pseudo
96
97[CSS Has Pseudo]: https://github.com/csstools/css-has-pseudo
98[Mutation Observer polyfill]: https://github.com/webmodules/mutation-observer
99[Selectors Level 4]: https://drafts.csswg.org/selectors-4/#has-pseudo
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