webpack.config.js

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

module.exports = (env) => {
  const isProduction = env === 'production';
  const CSSExtract = new ExtractTextPlugin('styles.css')
  //const envVars = dotenv.config().parsed;
  console.log(env);
  const envKeys = Object.keys(env).reduce((prev, next) => {
    prev[`process.env.${next}`] = JSON.stringify(env[next]);
    return prev;
  }, {});
  return {
    entry: './src/app.js',
    output: {
      path: path.join(__dirname, 'public', 'dist'),
      filename: 'bundle.js'
    },
    module: {
      rules: [
        {
          loader: 'babel-loader',
          test: /\.js$/,
          exclude: /node_modules/
        },
        {
          test: /\.s?css$/,
          use: CSSExtract.extract({
            use:
              [
                {
                  loader: 'css-loader',
                  options: {
                    sourceMap: true
                  }
                },
                {
                  loader: 'sass-loader',
                  options: {
                    sourceMap: true
                  }
                }
              ]
          })
        }
      ]
    },
    plugins: [
      CSSExtract,
      new webpack.DefinePlugin(envKeys)
    ],
    devtool: isProduction ? 'source-map' : 'inline-source-map',
    devServer: {
      contentBase: path.join(__dirname, 'public'),
      publicPath: '/dist/'
    }
  };
};