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-devUse 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 };
    }
  ]
});