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# CSS Blank Pseudo [<img src="http://jonathantneal.github.io/js-logo.svg" alt="" width="90" height="90" align="right">][CSS Blank 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 Blank Pseudo] lets you style form elements when they are empty, following
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the [Selectors Level 4] specification.
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```css
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input {
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/* style an input */
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}
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input:blank {
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/* style an input without a value */
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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 `:blank` selectors:
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```bash
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npx css-blank-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-blank-pseudo/browser"></script>
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<script>cssBlankPseudo(document)</script>
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```
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That’s it. The script is 509 bytes and works in all browsers.
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---
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If you support Internet Explorer 11, use the **browser legacy** script, which
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is 671 bytes:
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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-blank-pseudo/browser-legacy"></script>
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<script>cssBlankPseudo(document)</script>
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```
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## How it works
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The [PostCSS plugin](README-POSTCSS.md) clones rules containing `:blank`,
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replacing them with an alternative `[blank]` selector.
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```css
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input:blank {
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background-color: yellow;
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}
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/* becomes */
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input[blank] {
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background-color: yellow;
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}
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input:blank {
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background-color: yellow;
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}
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```
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Next, the [JavaScript library](README-BROWSER.md) adds a `blank` attribute to
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elements otherwise matching `:blank` natively.
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```html
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<input value="" blank>
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<input value="This element has a value">
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```
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[cli-img]: https://img.shields.io/travis/csstools/css-blank-pseudo/master.svg
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[cli-url]: https://travis-ci.org/csstools/css-blank-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-blank-pseudo.svg
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[npm-url]: https://www.npmjs.com/package/css-blank-pseudo
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[CSS Blank Pseudo]: https://github.com/csstools/css-blank-pseudo
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[PostCSS Preset Env]: https://preset-env.cssdb.org/
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[Selectors Level 4]: https://drafts.csswg.org/selectors-4/#blank
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