Include polyfills only if required by browser. (works with webpack)

conndtional-polyfill-with-webpack.js

// ___ Internal logic ___

/**
 * Indication does browser have all required methods for application to work without polyfills
 * @const {boolean}
 */
const ALL_FEATURES_SUPPORTED_BY_BROWSE = Boolean(window.Promise &&
  window.Array.from &&
  window.Array.prototype.includes &&
  window.Map &&
  window.Set &&
  window.Object.assign &&
  window.MutationObserver);

/**
 * Inject polyfill script to html document
 *
 * @param {Function} done - callback that will be called after polyfills have been loaded
 */
function loadPolyfills(done) {
  const js = document.createElement('script');
  js.src = 'polyfills.js';
  js.onload = done;
  document.head.appendChild(js);
}

/**
 * Load main application
 *
 */
function start() {
  require('./main'); // eslint-disable-line global-require
}

// ___ Execute Detection ___

if (ALL_FEATURES_SUPPORTED_BY_BROWSE) {
  start();
} else {
  loadPolyfills(start);
}