webpack.config.js

const path = require('path')
const webpack = require('webpack')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const DotEnv = require('dotenv-webpack')

module.exports = env => {

  return {
    entry: './src/index.js',
    output: {
      filename: 'bundle.js',
      path: path.resolve(__dirname, 'dist'),
      publicPath: '/'
    },
    module: {
      rules: [
        { test: /\.js$/, use: 'babel-loader', exclude: /node_modules/ },
        { test: /\.css$/, use: ['style-loader', 'css-loader'] },
        { test: /\.s(a|c)ss$/, use: ['style-loader', 'css-loader', 'sass-loader'] },
        { test: /\.(png|jpe?g|gif)$/i, use: 'file-loader' }
      ]
    },
    devServer: {
      publicPath: '/',
      contentBase: path.resolve('src'),
      hot: true,
      open: true,
      port: 8000,
      watchContentBase: true,
      historyApiFallback: true
    },
    plugins: [
      new DotEnv(),
      new webpack.HotModuleReplacementPlugin(),
      new HtmlWebpackPlugin({
        template: 'src/index.html',
        filename: 'index.html',
        inject: 'body'
      })
    ]
  }
}