滚动条定位

    backTop() {
　　　　//回到顶部
      let thisTOP = document.getElementsByClassName("router");
      thisTOP[0].scrollTop = 0;
    },
    replyToBottom(){
　　　　//回到底部
      let thisTOP = document.getElementsByClassName("router");
      var bottomPosition = thisTOP[0].scrollHeight;
      thisTOP[0].scrollTop = bottomPosition;
    },