IE 11 - Object doesn't support this action about formeo HOT 5 OPEN

export const createCustomEvent = (eventName, data) => {
  let event;
  if (typeof CustomEvent === 'function') {
    event = new CustomEvent(eventName, data);
  } else {
    event = document.createEvent('CustomEvent');
    event.initCustomEvent(eventName, true, true, data);
  }

  return event;
};

import {createCustomEvent} from './utils';
...
formeoSaved: createCustomEvent('formeoSaved', {}),
...

if (typeof Object.assign != 'function') {
  // Must be writable: true, enumerable: false, configurable: true
  Object.defineProperty(Object, 'assign', {
    value: function assign(target, varArgs) { // .length of function is 2
      'use strict';
      if (target == null) { // TypeError if undefined or null
        throw new TypeError('Cannot convert undefined or null to object');
      }

      let to = Object(target);

      for (let index = 1; index < arguments.length; index++) {
        let nextSource = arguments[index];

        if (nextSource != null) { // Skip over if undefined or null
          for (let nextKey in nextSource) {
            // Avoid bugs when hasOwnProperty is shadowed
            if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
              to[nextKey] = nextSource[nextKey];
            }
          }
        }
      }
      return to;
    },
    writable: true,
    configurable: true
  });
}