postcss-custom-media

What is postcss-custom-media?

The postcss-custom-media package allows you to define custom media queries in CSS, which can then be reused throughout your stylesheets. This helps in maintaining a consistent and DRY (Don't Repeat Yourself) approach to media queries.

What are postcss-custom-media's main functionalities?

Define Custom Media Queries

This feature allows you to define custom media queries using the @custom-media rule. In this example, a custom media query named --small-viewport is defined for viewports with a maximum width of 30em.

@custom-media --small-viewport (max-width: 30em);

Use Custom Media Queries

Once a custom media query is defined, it can be used in your CSS just like any other media query. In this example, the custom media query --small-viewport is used to change the text color to red for small viewports.

body { color: black; }
@media (--small-viewport) { body { color: red; } }

Other packages similar to postcss-custom-media

postcss-preset-env

postcss-preset-env allows you to use future CSS features today by converting modern CSS into something most browsers can understand. It includes a variety of plugins, including the ability to use custom media queries. Compared to postcss-custom-media, postcss-preset-env offers a broader range of features but may be overkill if you only need custom media queries.

postcss-media-minmax

postcss-media-minmax lets you write simpler and more concise media queries by using the < and > operators. While it doesn't offer custom media queries, it simplifies the syntax of media queries, making them easier to read and write. It is a good alternative if you are looking for a way to simplify your media queries without defining custom ones.

README

PostCSS Custom Media

PostCSS Custom Media lets you define @custom-media in CSS following the Custom Media Specification.

@custom-media --small-viewport (max-width: 30em);

@media (--small-viewport) {
	/* styles for small viewport */
}

/* becomes */

@media (max-width: 30em) {
	/* styles for small viewport */
}

Usage

Add PostCSS Custom Media to your project:

npm install postcss postcss-custom-media --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssCustomMedia = require('postcss-custom-media');

postcss([
	postcssCustomMedia(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);

PostCSS Custom Media runs in all Node environments, with special instructions for:

Node	PostCSS CLI	Webpack	Create React App	Gulp	Grunt

Options

preserve

The preserve option determines whether the original notation is preserved. By default, it is not preserved.

postcssCustomMedia({ preserve: true })

@custom-media --small-viewport (max-width: 30em);

@media (--small-viewport) {
	/* styles for small viewport */
}

/* becomes */

@custom-media --small-viewport (max-width: 30em);

@media (max-width: 30em) {
	/* styles for small viewport */
}

@media (--small-viewport) {
	/* styles for small viewport */
}

importFrom

The importFrom option specifies sources where custom media can be imported from, which might be CSS, JS, and JSON files, functions, and directly passed objects.

postcssCustomMedia({
	importFrom: 'path/to/file.css' // => @custom-selector --small-viewport (max-width: 30em);
});

@media (max-width: 30em) {
	/* styles for small viewport */
}

@media (--small-viewport) {
	/* styles for small viewport */
}

Multiple sources can be passed into this option, and they will be parsed in the order they are received. JavaScript files, JSON files, functions, and objects will need to namespace custom media using the customMedia or custom-media key.

postcssCustomMedia({
	importFrom: [
		'path/to/file.css',
		'and/then/this.js',
		'and/then/that.json',
		{
			customMedia: { '--small-viewport': '(max-width: 30em)' }
		},
		() => {
			const customMedia = { '--small-viewport': '(max-width: 30em)' };

			return { customMedia };
		}
	]
});

exportTo

The exportTo option specifies destinations where custom media can be exported to, which might be CSS, JS, and JSON files, functions, and directly passed objects.

postcssCustomMedia({
	exportTo: 'path/to/file.css' // @custom-media --small-viewport (max-width: 30em);
});

Multiple destinations can be passed into this option, and they will be parsed in the order they are received. JavaScript files, JSON files, and objects will need to namespace custom media using the customMedia or custom-media key.

const cachedObject = { customMedia: {} };

postcssCustomMedia({
	exportTo: [
		'path/to/file.css',   // @custom-media --small-viewport (max-width: 30em);
		'and/then/this.js',   // module.exports = { customMedia: { '--small-viewport': '(max-width: 30em)' } }
		'and/then/this.mjs',  // export const customMedia = { '--small-viewport': '(max-width: 30em)' } }
		'and/then/that.json', // { "custom-media": { "--small-viewport": "(max-width: 30em)" } }
		cachedObject,
		customMedia => {
			customMedia    // { '--small-viewport': '(max-width: 30em)' }
		}
	]
});

See example exports written to CSS, JS, MJS, and JSON.