code: function setupEventListeners(reference, options, state, updateBound) {
    // Resize event listener on window
    state.updateBound = updateBound;
    getWindow(reference).addEventListener('resize', state.updateBound, { passive: true });
  
    // Scroll event listener on scroll parents
    var scrollElement = getScrollParent(reference);
    attachToScrollParents(scrollElement, 'scroll', state.updateBound, state.scrollParents);
    state.scrollElement = scrollElement;
    state.eventsEnabled = true;
  
    return state;
  }
docs: Setup needed event listeners used to update the popper position
  @method
  @memberof Popper.Utils
  @private