webpack.prod.conf.js

const path = require('path');

const CleanWebpackPlugin = require('clean-webpack-plugin');
const CopyWebpackPlugin = require('copy-webpack-plugin');

module.exports = {
  entry: {
    app: [
      './src/index'
    ],
    vendor: [
      "@webcomponents/webcomponentsjs/custom-elements-es5-adapter",
      "@webcomponents/webcomponentsjs/webcomponents-loader"
    ]
  },
  resolve: {
    modules: ["node_modules"],
  },
  output: {
    filename: '[name].js',
    path: path.resolve(__dirname, 'dist')
  },
  module: {
    rules: [
      {
        test: /\.ts?$/,
        use: 'ts-loader',
        exclude: /node_modules/
      }
    ]
  },
  resolve: {
    extensions: ['.ts', '.js']
  },
  plugins: [
    new CleanWebpackPlugin(['dist'], { verbose: true, root: path.resolve(__dirname) }),
    new CopyWebpackPlugin([
      {
        from: path.join(
          path.resolve(__dirname, './node_modules/@webcomponents/webcomponentsjs/'),
          '*.js'
        ),
        to: './webcomponentjs',
        flatten: true
      }
    ])
  ]
};