PostCSS Environment Variables

PostCSS Environment Variables lets you use env() variables in CSS, following the CSS Environment Variables specification.

@media (max-width: env(--branding-small)) {
  body {
    padding: env(--branding-padding);
  }
}

/* becomes */

@media (min-width: 600px) {
  body {
    padding: 20px;
  }
}

/* when the `importFrom` option is: {
  "environmentVariables": {
    "--branding-small": "600px",
    "--branding-padding": "20px"
  }
} */

Usage

Add PostCSS Environment Variables to your project:

npm install postcss postcss-env-function --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss')
const postcssEnvFunction = require('postcss-env-function')

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

PostCSS Environment Variables runs in all Node environments, with special instructions for:

Node	PostCSS CLI	Webpack	Create React App	Gulp	Grunt

Options

importFrom

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

postcssEnvFunction({
  importFrom: 'path/to/file.js' /* module.exports = {
      environmentVariables: {
        '--branding-padding': '20px',
        '--branding-small': '600px'
      }
    } */
})

@media (max-width: env(--branding-small)) {
  body {
    padding: env(--branding-padding);
  }
}

/* becomes */

@media (min-width: 600px) {
  body {
    padding: 20px;
  }
}

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 Properties using the environmentVariables or environment-variables key.

postcssEnvFunction({
  importFrom: [
    /* Import from a CommonJS file:
    
    module.exports = {
      environmentVariables: {
        '--branding-padding': '20px'
      }
    } */
    'path/to/file.js',

    /* Import from a JSON file:

    {
      "environment-variables": {
        "--branding-padding": "20px"
      }
    } */
    'and/then/this.json',

    /* Import from an JavaScript Object: */
    {
      environmentVariables: { '--branding-padding': '20px' }
    },

    /* Import from a JavaScript Function: */
    () => {
      const environmentVariables = { '--branding-padding': '20px' }

      return { environmentVariables }
    }
  ]
})

See example imports written in JS and JSON. Currently only valid custom property names (beginning with --) are accepted. Not all valid declaration value names are accepted.