Function createCustomEvent

src/utils/event-helper.js:21–39

(win, type, detail, opt_eventInit)

 * @return {!Event}
 */
export function createCustomEvent(win, type, detail, opt_eventInit) {
  const eventInit = /** @type {!CustomEventInit} */ ({detail});
  Object.assign(eventInit, opt_eventInit);
  // win.CustomEvent is a function on Edge, Chrome, FF, Safari but
  // is an object on IE 11.
  if (mode.isEsm() || typeof win.CustomEvent == 'function') {
    return new win.CustomEvent(type, eventInit);
  } else {
    // Deprecated fallback for IE.
    const e = win.document.createEvent('CustomEvent');
    e.initCustomEvent(
      type,
      !!eventInit.bubbles,
      !!eventInit.cancelable,
      detail
    );
    return e;
  }
}

/**
 * Listens for the specified event on the element.