purgecss for rails

postcss.config.js

const purgecss = require('@fullhuman/postcss-purgecss')({
  content: [
    './app/**/*.html.erb',
    './app/helpers/**/*.rb',
    './app/javascript/**/*.js',
  ],
  defaultExtractor: content => {
    const broadMatches = content.match(/[^<>"'`\s]*[^<>"'`\s:]/g) || []
    const innerMatches = content.match(/[^<>"'`\s.()]*[^<>"'`\s.():]/g) || []
    return broadMatches.concat(innerMatches)
  }
})


module.exports = {
  plugins: [
    require('postcss-import'),
    require('postcss-flexbugs-fixes'),
    require('postcss-preset-env')({
      autoprefixer: {
        flexbox: 'no-2009'
      },
      stage: 3
    }),
    ...process.env.NODE_ENV === 'production'
      ? [purgecss]
      : []
  ]
}