_lazyLoadHandler () {
      const freeList = []
      this.ListenerQueue.forEach((listener, index) => {
        if (!listener.el || !listener.el.parentNode) {
          freeList.push(listener)
        }
        const catIn = listener.checkInView()
        if (!catIn) return
        listener.load()
      })
      freeList.forEach(item => {
        remove(this.ListenerQueue, item)
        item.$destroy()
      })
    }
find nodes which in viewport and trigger load
@return