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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]
[![NPM Version][npm-img]][npm-url]
[<img alt="Discord" src="https://shields.io/badge/Discord-5865F2?logo=discord&logoColor=white">][discord]
[CSS Blank Pseudo] lets you style form elements when they are empty, following
the [Selectors Level 4] specification.
```css
input {
/* style an input */
}
input:blank {
/* style an input without a value */
}
```
## Usage
From the command line, transform CSS files that use `:blank` selectors:
```bash
npx css-blank-pseudo SOURCE.css --output TRANSFORMED.css
```
Next, use your transformed CSS with this script:
```html
<link rel="stylesheet" href="TRANSFORMED.css">
<script src="https://unpkg.com/css-blank-pseudo/dist/browser-global.js"></script>
<script>cssBlankPseudo(document)</script>
```
Please use a versioned url, like this : `https://unpkg.com/css-blank-pseudo@3.0.0/dist/browser-global.js`
Without the version, you might unexpectedly get a new major version of the library with breaking changes.
If you were using an older version via a CDN, please update the entire url.
The old URL will no longer work in a future release.
That’s it. The script works in most browsers.
## How it works
The [PostCSS plugin](README-POSTCSS.md) clones rules containing `:blank`,
replacing them with an alternative `[blank]` selector.
```css
input:blank {
background-color: yellow;
}
/* becomes */
input[blank] {
background-color: yellow;
}
input:blank {
background-color: yellow;
}
```
Next, the [JavaScript library](README-BROWSER.md) adds a `blank` attribute to
elements otherwise matching `:blank` natively.
```html
<input value="" blank>
<input value="This element has a value">
```
## ⚠ `:not(:blank)`
with option : `preserve` `true`
```css
input:not(:blank) {
background-color: yellow;
}
/* becomes */
input:not([blank]) {
background-color: yellow;
}
input:not(:blank) {
background-color: yellow;
}
```
When you do not include the JS polyfill one will always match in browsers that support `:blank` natively.
In browsers that do not support `:blank` natively the rule will be invalid.
_currently no browsers support `:blank`_
[discord]: https://discord.gg/bUadyRwkJS
[npm-img]: https://img.shields.io/npm/v/css-blank-pseudo.svg
[npm-url]: https://www.npmjs.com/package/css-blank-pseudo
[CSS Blank Pseudo]: https://github.com/csstools/postcss-plugins/tree/main/plugins/css-blank-pseudo
[PostCSS Preset Env]: https://preset-env.cssdb.org/
[Selectors Level 4]: https://drafts.csswg.org/selectors-4/#blank