polyfill-customEvent.js

try {
  new CustomEvent("IE has CustomEvent, but doesn't support constructor");
} catch (e) {

  window.CustomEvent = function(event, params) {
    var evt;
    params = params || {
      bubbles: false,
      cancelable: false,
      detail: undefined
    };
    evt = document.createEvent("CustomEvent");
    evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail);
    return evt;
  };

  CustomEvent.prototype = Object.create(window.Event.prototype);
}