     setTimeout(() => {
        const clone = document.querySelector('video').cloneNode(true)
        document.querySelector('#div3').appendChild(clone)
      }, 3000)

      const mo = new MutationObserver(records => {
        records.forEach(record => {
          record.addedNodes.forEach(addedNode => {
            if (addedNode instanceof HTMLVideoElement){
              console.log("video element added!", addedNode)
              observeVideo(addedNode)
            }
          })
        })
      })
   