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# CSS Has Pseudo [<img src="http://jonathantneal.github.io/js-logo.svg" alt="" width="90" height="90" align="right">][CSS Has Pseudo]
[![NPM Version][npm-img]][npm-url][![Build Status][cli-img]][cli-url][![Support Chat][git-img]][git-url]
[CSS Has Pseudo] lets you style elements relative to other elements in CSS,following the [Selectors Level 4] specification.
```cssa:has(> img) { /* style links that contain an image */}
h1:has(+ p) { /* style level 1 headings that are followed by a paragraph */}
section:not(:has(h1, h2, h3, h4, h5, h6)) { /* style sections that don’t contain any heading elements */}
body:has(:focus) { /* style the body if it contains a focused element */}```
## Usage
From the command line, transform CSS files that use `:has` selectors:
```bashnpx css-has-pseudo SOURCE.css TRANSFORMED.css```
Next, use your transformed CSS with this script:
```html<link rel="stylesheet" href="TRANSFORMED.css"><script src="https://unpkg.com/css-has-pseudo/browser"></script><script>cssHasPseudo(document)</script>```
That’s it. The script is 765 bytes and works in all browsers, includingInternet Explorer 11. With a [Mutation Observer polyfill], the script will workdown to Internet Explorer 9.
## How it works
The [PostCSS plugin](README-POSTCSS.md) clones rules containing `:has`,replacing them with an alternative `[:has]` selector.
```cssbody:has(:focus) { background-color: yellow;}
section:not(:has(h1, h2, h3, h4, h5, h6)) { background-color: gray;}
/* becomes */
body[\:has\(\:focus\)] { background-color: yellow;}
body:has(:focus) { background-color: yellow;}
section[\:not-has\(h1\,\%20h2\,\%20h3\,\%20h4\,\%20h5\,\%20h6\)] { background-color: gray;}
section:not(:has(h1, h2, h3, h4, h5, h6)) { background-color: gray;}```
Next, the [JavaScript library](README-BROWSER.md) adds a `[:has]` attribute toelements otherwise matching `:has` natively.
```html<body :has(:focus)> <input value="This element is focused"></body>```
[cli-img]: https://img.shields.io/travis/csstools/css-has-pseudo/master.svg[cli-url]: https://travis-ci.org/csstools/css-has-pseudo[git-img]: https://img.shields.io/badge/support-chat-blue.svg[git-url]: https://gitter.im/postcss/postcss[npm-img]: https://img.shields.io/npm/v/css-has-pseudo.svg[npm-url]: https://www.npmjs.com/package/css-has-pseudo
[CSS Has Pseudo]: https://github.com/csstools/css-has-pseudo[Mutation Observer polyfill]: https://github.com/webmodules/mutation-observer[Selectors Level 4]: https://drafts.csswg.org/selectors-4/#has-pseudo
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