css-blank-pseudo
v7.0.1
Published
Style form elements when they are empty
Downloads
23,918,702
Readme
PostCSS Blank Pseudo
npm install css-blank-pseudo --save-dev
PostCSS Blank Pseudo lets you style form elements when they are empty, following the Selectors Level 4 specification.
To use this feature you need to do two things :
- add the PostCSS plugin that transforms the selector into a class or attribute
- add the browser polyfill that sets the attribute or class on elements in a browser
input:blank {
background-color: yellow;
}
/* becomes */
input[blank].js-blank-pseudo, .js-blank-pseudo input[blank] {
background-color: yellow;
}
input:blank {
background-color: yellow;
}
Usage
Add PostCSS Blank Pseudo to your project:
npm install postcss css-blank-pseudo --save-dev
Use it as a PostCSS plugin:
const postcss = require('postcss');
const postcssBlankPseudo = require('css-blank-pseudo');
postcss([
postcssBlankPseudo(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);
Options
preserve
The preserve
option determines whether the original notation
is preserved. By default, it is preserved.
postcssBlankPseudo({ preserve: false })
input:blank {
background-color: yellow;
}
/* becomes */
input[blank].js-blank-pseudo, .js-blank-pseudo input[blank] {
background-color: yellow;
}
replaceWith
The replaceWith
option determines the selector to use when replacing
the :blank
pseudo. By default is [blank]
postcssBlankPseudo({ replaceWith: '.css-blank' })
input:blank {
background-color: yellow;
}
/* becomes */
.foo {
color: blue;
color: red;
}
.baz {
color: green;
}
Note that changing this option implies that it needs to be passed to the browser polyfill as well.
disablePolyfillReadyClass
The disablePolyfillReadyClass
option determines if selectors are prefixed with an indicator class.
This class is only set on your document if the polyfill loads and is needed.
By default this option is false
.
Set this to true
to prevent the class from being added.
postcssBlankPseudo({ disablePolyfillReadyClass: true })
input:blank {
background-color: yellow;
}
/* becomes */
input[blank] {
background-color: yellow;
}
input:blank {
background-color: yellow;
}
Browser
import cssBlankPseudoInit from 'css-blank-pseudo/browser';
cssBlankPseudoInit();
or
<!-- When using a CDN url you will have to manually update the version number -->
<script src="https://unpkg.com/[email protected]/dist/browser-global.js"></script>
<script>cssBlankPseudoInit()</script>
PostCSS Blank Pseudo works in all major browsers, including Safari 6+ and Internet Explorer 9+ without any additional polyfills.
This plugin conditionally uses MutationObserver
to ensure recently inserted
inputs get correct styling upon insertion. If you intend to rely on that
behaviour for browsers that do not support MutationObserver
, you have two
options:
- Polyfill
MutationObserver
. As long as it runs beforecssBlankPseudoInit
, the polyfill will work. - If you don't want to polyfill
MutationObserver
you can also manually fire achange
event upon insertion so they're automatically inspected by the polyfill.
Browser Usage
force
The force
option determines whether the library runs even if the browser
supports the selector or not. By default, it won't run if the browser does
support the selector.
cssBlankPseudoInit({ force: true });
replaceWith
Similar to the option for the PostCSS Plugin, replaceWith
determines the
attribute or class to apply to an element when it's considered to be :blank
.
cssBlankPseudoInit({ replaceWith: '.css-blank' });
This option should be used if it was changed at PostCSS configuration level.
Please note that using a class, leverages classList
under the hood which
might not be supported on some old browsers such as IE9, so you may need
to polyfill classList
in those cases.
Using with Next.js
Given that Next.js imports packages both on the browser and on the server, you need to make sure that the package is only imported on the browser.
As outlined in the Next.js documentation, you need to load the package with a dynamic import:
useEffect(async () => {
const cssBlankPseudoInit = (await import('css-blank-pseudo/browser')).default;
cssBlankPseudoInit();
}, []);
We recommend you load the polyfill as high up on your Next application as possible, such as your pages/_app.ts
file.