ice.fo.utils/server_side/CssUtils.js

const CleanCSS = require('clean-css')

exports.minifyCss = function minifyCSS (content) {
  return new CleanCSS({
    level: {
      2: {
        mergeAdjacentRules: true, // controls adjacent rules merging; defaults to true
        mergeIntoShorthands: true, // controls merging properties into shorthands; defaults to true
        mergeMedia: true, // controls `@media` merging; defaults to true
        mergeNonAdjacentRules: true, // controls non-adjacent rule merging; defaults to true
        mergeSemantically: false, // controls semantic merging; defaults to false
        overrideProperties: true, // controls property overriding based on understandability; defaults to true
        removeEmpty: true, // controls removing empty rules and nested blocks; defaults to `true`
        reduceNonAdjacentRules: true, // controls non-adjacent rule reducing; defaults to true
        removeDuplicateFontRules: true, // controls duplicate `@font-face` removing; defaults to true
        removeDuplicateMediaBlocks: true, // controls duplicate `@media` removing; defaults to true
        removeDuplicateRules: true, // controls duplicate rules removing; defaults to true
        removeUnusedAtRules: false, // controls unused at rule removing; defaults to false (available since 4.1.0)
        restructureRules: false, // controls rule restructuring; defaults to false
        skipProperties: [], // controls which properties won't be optimized, defaults to `[]` which means all will be optimized (since 4.1.0)
      },
    },

  }).minify(content).styles
}