utils/events.js
function addDelegatedListener(el, type, listener) {
  incrementListenerCount(listener);
  return el.addEventListener(type, getDelegateFunction_(listener));
}
function addDelegatedListener(el, type, listener) {
  incrementListenerCount(listener);
  return el.addEventListener(type, getDelegateFunction_(listener));
}
function addDelegatedListener ( el , type , listener ) { incrementListenerCount ( listener ) ; return el . addEventListener ( type , getDelegateFunction_ ( listener ) ) ; }
Adds an event listener to an element where the event target
is discovered by moving up the clicked element's descendants.
@param {Element} el Element to host the listener.
@param {string} type Listener type.
@param {Function} listener Listener function.
Adds an event listener to an element where the event target is discovered by moving up the clicked element s descendants .