Function on

Sortable.js:137–139

(el, event, fn)

    passive: false
  };
  function on(el, event, fn) {
    el.addEventListener(event, fn, !IE11OrLess && captureMode);
  }
  function off(el, event, fn) {
    el.removeEventListener(event, fn, !IE11OrLess && captureMode);
  }