Function addEvent

scripts/smoothScroll.js:702–704

* HELPERS

(type, fn, arg)

   * HELPERS
   ***********************************************/
  function addEvent(type, fn, arg) {
    window.addEventListener(type, fn, arg || false);
  }
  function removeEvent(type, fn, arg) {
    window.removeEventListener(type, fn, arg || false);
  }