fab-manager/app/frontend/src/javascript/lib/polyfill.js

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');
      }

      const to = Object(target);

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

        if (nextSource != null) { // Skip over if undefined or null
          for (const 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
  });
}

Number.isInteger = Number.isInteger || function (value) {
  return typeof value === 'number' &&
    isFinite(value) &&
    Math.floor(value) === value;
};