# PostCSS Custom Media

[![NPM Version](https://img.shields.io/npm/v/postcss-custom-media.svg)](https://www.npmjs.com/package/postcss-custom-media) [![CSS Standard Status](https://cssdb.org/badge/custom-media-queries.svg)](https://cssdb.org/#custom-media-queries) [![Build Status](https://img.shields.io/travis/postcss/postcss-custom-media/master.svg)](https://travis-ci.org/postcss/postcss-custom-media) [![Support Chat](https://img.shields.io/badge/support-chat-blue.svg)](https://gitter.im/postcss/postcss)

[PostCSS Custom Media](https://github.com/postcss/postcss-custom-media) lets you use Custom Media Queries in CSS, following the [CSS Media Queries](https://drafts.csswg.org/mediaqueries-5/#custom-mq) 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](https://github.com/postcss/postcss-custom-media) to your project:

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

Use [PostCSS Custom Media](https://github.com/postcss/postcss-custom-media) to process your CSS:

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

postcssCustomMedia.process(YOUR_CSS /*, processOptions, pluginOptions */);
```

Or use it as a [PostCSS](https://github.com/postcss/postcss) plugin:

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

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

[PostCSS Custom Media](https://github.com/postcss/postcss-custom-media) runs in all Node environments, with special instructions for:

| [Node](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/INSTALL.md#node) | [PostCSS CLI](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/INSTALL.md#postcss-cli) | [Webpack](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/INSTALL.md#webpack) | [Create React App](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/INSTALL.md#create-react-app) | [Gulp](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/INSTALL.md#gulp) | [Grunt](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/INSTALL.md#grunt) |
| ---------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |

## Options

### preserve

The `preserve` option determines whether custom media and atrules using custom media should be preserved in their original form.

```
@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.

```js
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.

```js
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.

```js
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.

```js
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](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/test/export-media.css), [JS](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/test/export-media.js), [MJS](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/test/export-media.mjs), and [JSON](https://github.com/bgoonz/Learning-Redux/blob/master/repos/examples/real-world/node_modules/postcss-custom-media/test/export-media.json).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://bryan-guner.gitbook.io/my-docs/redux/repos/examples/real-world/node_modules/postcss-custom-media.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.