package.json

{
  "name": "webpack-aula",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev": "webpack",
    "production": "NODE_ENV=production webpack",
    "watch": "npm run dev -- --watch"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-core": "^6.24.1",
    "babel-loader": "^7.0.0",
    "babel-preset-es2015": "^6.24.1",
    "css-loader": "^0.28.4",
    "extract-text-webpack-plugin": "^2.1.0",
    "file-loader": "^0.11.1",
    "node-sass": "^4.5.3",
    "purify-css": "^1.2.2",
    "purifycss-webpack": "^0.7.0",
    "raw-loader": "^0.5.1",
    "sass-loader": "^6.0.5",
    "style-loader": "^0.18.1",
    "webpack": "^2.6.1"
  }
}

webpack.config.js

var webpack = require('webpack');
var path = require('path');
var glob = require('glob');
var ExtractTextPlugin = require("extract-text-webpack-plugin");
let PurifyCSSPlugin = require('purifycss-webpack');

var inProduction = (process.env.NODE_ENV === 'production');

module.exports = {
    entry: {
      app: [
        './src/main.js',
        './src/main.scss'
      ]
    },

    output: {
      path: path.resolve(__dirname, './dist'),
      filename: '[name].js'
    },

    module: {
      rules: [
        {
          test: /\.s[ac]ss$/,
          use: ExtractTextPlugin.extract({
            use: ['css-loader', 'sass-loader'],
            fallback: 'style-loader'
          })
        },

        {
          test: /\.png|jpe?g|svg$/,
          loader: 'file-loader',
          options: {
            name: 'images/[name][hash].[ext]'
          }
        },

        {
          test: /\.js$/,
          exclude: /node_modules/,
          loader: "babel-loader"
        }
      ]
    },

    plugins: [
      new ExtractTextPlugin('[name].css'),

      new PurifyCSSPlugin({
        paths: glob.sync(path.join(__dirname, '**/*.html')),
        minimize: inProduction
      }),

      new webpack.LoaderOptionsPlugin({
        minimize: inProduction
      })
    ]
};

if (inProduction) {
  module.exports.plugins.push(
    new webpack.optimize.UglifyJsPlugin()
  );
}