[SuperZen]

<div id='main'></div>
<div id='out' style="color:red"></div>
<button id='add'>add item</button>
<button id='remove'>remove last</button>
<script>
  var callback = (mutationsList) => {
    for (var mutation of mutationsList) {
      // если добавление или удаление Node
      if (mutation.type === 'childList') { // если добавление
        if (mutation.addedNodes.length > 0) {
          let [firstnode] = mutation.addedNodes
          firstnode.addEventListener('click', click)
        } else if (mutation.removedNodes.length > 0) { // если удаление
          let [firstnode] = mutation.removedNodes
          firstnode.removeEventListener('click', click)
        }
      }
    }
  }

  var main = document.getElementById('main')
  var observer = new MutationObserver(callback)
  var config = { attributes: false, childList: true, subtree: false }
  observer.observe(main, config)
  var click = (e) => document.getElementById('out').innerHTML = e.target.id

  document.getElementById('add').addEventListener('click', (e) => {
    var item = document.createElement('div')
    item.id = `item ${main.querySelectorAll('*').length}`
    item.innerHTML = item.id
    main.appendChild(item)
  })

  document.getElementById('remove').addEventListener('click', (e) => {
    var items = main.querySelectorAll('*')
    items.length > 0 && main.removeChild(items[items.length - 1])
  })
</script>