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