vue-scroll滚动判断是否滚动到底部滚动方向获取滚动区域dom元素

1、是否滚动到底部

 isScrollBottom() {      // 是否滚动到了底部      this.box = this.$refs.chatListWrapper      var clientHeight = this.box.clientHeight      var scrollTop = this.box.scrollTop      var scrollHeight = this.box.scrollHeight      if (scrollTop + clientHeight == scrollHeight) {        this.$store.dispatch('setBottomBtn', false, { root: true }) // 隐藏直达最新消息按钮        this.isBottom = true        this.isTop = false      } else {        this.$store.dispatch('setBottomBtn', true, { root: true }) // 显示直达最新消息按钮        this.isTop = false        this.isBottom = false        if (scrollTop == 0) {          this.isTop = true        }      }    },

2、scroll滚动方向判断

    getDirection() {      // scroll滚动方向~~~~      this.box = this.$refs.chatListWrapper      var scrollTop = this.box.scrollTop      var scroll = scrollTop - this.initTop      this.initTop = scrollTop      let dir = 'down'      if (scroll < 0) {        dir = 'up'      } else {        dir = 'down'      }      return dir    },

3、滚动节流
1）、在滚动的dom上绑定scroll事件，监听滚动

2）、data中定义：fnScroll: () => {}, 初始值
3）、mounted中给fnScroll函数赋值，_.throttle实现滚动节流

this.fnScroll = _.throttle(() => {}, 500)

4、获取滚动可视区域内dom：实现注意：判断当前元素是否在可视区域内，若在则存到isSeeDomArr中，然后循环isSeeDomArr数组，拿到当前可视区域内的最后一个dom,再去判断是否更新对应的咨询轨迹。
不要滚动时就去更新，这样会造成不停请求更新，最后一次请求可能无效，造成数据的错乱

    sendRead() {      const chatLi = document        .getElementById('chat_list_wrapper')        .getElementsByTagName('li')      var container = this.$refs.chatListWrapper      var swHeight = container.clientHeight      const scrollTop = container.scrollTop      const aa = swHeight + scrollTop      let isSeeDomArr = []      for (let j = 0; j < chatLi.length; j++) {        if (scrollTop < chatLi[j].offsetTop && chatLi[j].offsetTop < aa) {          isSeeDomArr.push(chatLi[j]) //将可视区域内所有dom存储到isSeeDomArr        }      }      if (isSeeDomArr.length) {        // 非 ceo接诊台更新消息的已读状态        if (this.$route.path.indexOf('diagnose/ceo') === -1) {          for (let m = 0; m < isSeeDomArr.length; m++) {            const isSelfSend = isSeeDomArr[m].getAttribute('isSelfSend')            const msgStatus = isSeeDomArr[m].getAttribute('msgStatus')            const msgType = isSeeDomArr[m].getAttribute('msgType')            if (!isSelfSend && !msgStatus && msgType !== 'notice') {              const _id = isSeeDomArr[m].getAttribute('id')              this.sendReadApi(_id)            }          }        }        // 更新聊天对应的咨询轨迹        this.setCurrentFdAsk(          isSeeDomArr[isSeeDomArr.length - 1].getAttribute('fdAsk')        )      }    },

the end：滚动加载这些判断前前后后改了好多次，这次终于感觉逻辑比较清晰了，也算对自己有个交代。。。