webpack.config.js

const path = require('path');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const CopyWebpackPlugin = require('copy-webpack-plugin');

module.exports = {
  entry: './js/app.js',
  stats: {
    colors: true,
    children: false,
    modules: false,
    hash: false,
    version: false,
    excludeAssets: (source) => {
      return ["app.js", "../css/app.css"].indexOf(source) === -1;
    }
  },
  output: {
    filename: 'app.js',
    path: path.resolve(__dirname, '../priv/static/js')
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader'
        }
      },
      {
        test: /\.css$/,
        use: ExtractTextPlugin.extract({
          fallback: 'style-loader',
          use: 'css-loader'
        })
      }
    ]
  },
  plugins: [
    new ExtractTextPlugin('../css/app.css'),
    new CopyWebpackPlugin([{ from: 'static/', to: '../' }])
  ]
};