css-utils.js

var
  ExtractTextPlugin = require('extract-text-webpack-plugin'),
  autoprefixer = require('autoprefixer'),
  purify = require('purify-css'),
  glob = require('glob'),
  path = require('path'),
  fs = require('fs')

module.exports.postcss = [autoprefixer()]

module.exports.styleLoaders = function (options) {
  options = options || {}

  function generateLoaders (loaders) {
    if (options.postcss) {
      loaders.splice(1, 0, 'postcss')
    }

    var sourceLoader = loaders.map(function (loader) {
      var extraParamChar
      if (/\?/.test(loader)) {
        loader = loader.replace(/\?/, '-loader?')
        extraParamChar = '&'
      }
      else {
        loader = loader + '-loader'
        extraParamChar = '?'
      }
      return loader + (options.sourceMap ? extraParamChar + 'sourceMap' : '')
    }).join('!')

    if (options.extract) {
      return ExtractTextPlugin.extract({
        use: sourceLoader,
        fallback: 'vue-style-loader'
      })
    }
    else {
      return ['vue-style-loader', sourceLoader].join('!')
    }
  }

  return {
    css: generateLoaders(['css']),
    less: generateLoaders(['css', 'less']),
    sass: generateLoaders(['css', 'sass?indentedSyntax']),
    scss: generateLoaders(['css', 'sass']),
    styl: generateLoaders(['css', 'stylus']),
    stylus: generateLoaders(['css', 'stylus'])
  }
}

module.exports.styleRules = function (options) {
  var output = []
  var loaders = exports.styleLoaders(options)
  for (var extension in loaders) {
    var loader = loaders[extension]
    output.push({
      test: new RegExp('\\.' + extension + '$'),
      loader: loader
    })
  }
  return output
}

function getSize (size) {
  return (size / 1024).toFixed(2) + 'kb'
}

module.exports.purify = function(cb) {
  var css = glob.sync(path.join(__dirname, '../dist/**/*.css'))
  var js = glob.sync(path.join(__dirname, '../dist/**/*.js'))

  Promise.all(css.map(function (file) {
    return new Promise(function (resolve) {
      console.log('\n Purifying ' + path.relative(path.join(__dirname, '../dist'), file).bold + '...')
      purify(js, [file], {minify: true}, function (purified) {
        var oldSize = fs.statSync(file).size
        fs.writeFileSync(file, purified)
        var newSize = fs.statSync(file).size

        console.log(
          ' * Reduced size by ' + ((1 - newSize / oldSize) * 100).toFixed(2) + '%, from ' +
          getSize(oldSize) + ' to ' + getSize(newSize) + '.'
        )
        resolve()
      })
    })
  }))
  .then(cb)
}