webpack.config.js

var webpack = require('webpack');
var HtmlWebpackPlugin = require('html-webpack-plugin');

var config = {
  context: __dirname + '/src', // `__dirname` is root of project and `src` is source
  entry: {
    app: './app.js',
  },
  output: {
    path: __dirname + '/dist', // `dist` is the destination
    filename: 'bundle.js',
  },
  module: {
    rules: [
      {
        test: /\.js$/, //Check for all js files
        loader: 'babel-loader',
        query: {
          presets: [ "babel-preset-es2015" ].map(require.resolve)
        }
      }
    ]
  },
  plugins: [new HtmlWebpackPlugin({
    hash: true,
    title: 'Basic MSE Sample',
    template: 'assets/index.html'
  })],
  devServer: {
    open: true, // to open the local server in browser
    contentBase: [
        'assets'
    ]
  },
  devtool: "eval-source-map" // Default development sourcemap
};

// Check if build is running in production mode, then change the sourcemap type
if (process.env.NODE_ENV === "production") {
    config.devtool = "source-map";
}

module.exports = config;