contact.js

// npm install fs-extra concat --save-dev
// place this file in the root of project next to angular.json

const fs = require('fs-extra');
const concat = require('concat');
(async function build() {
  const files = [
    './dist/app/runtime.js',
    './dist/app/polyfills.js',
    './dist/app/main.js',
  ]
  await fs.ensureDir('elements')
  await concat(files, './elements/counter.js');
  await fs.copy('./dist/app/styles.css', 'elements/styles.css')
})();

// Add this line to package.json under script
"build:elements": "ng build --prod --output-hashing none && node concatenate.js"

// npm run build:elements