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-env-function --save-dev

Use PostCSS Environment Variables to process your CSS:

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

postcssEnvFunction.process(YOUR_CSS /*, processOptions, pluginOptions */);

Or 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.

postcssCustomProperties({
  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 variables-variables key.

postcssCustomProperties({
  importFrom: [
    'path/to/file.js', // module.exports = { environmentVariables: { '--branding-padding': '20px' } }
    'and/then/this.json', // { "environment-variables": { "--branding-padding": "20px" } }
    {
      environmentVariables: { '--branding-padding': '20px' }
    },
    () => {
      const environmentVariables = { '--branding-padding': '20px' };

      return { environmentVariables };
    }
  ]
});

See example imports written in JS and JSON.