<template> <div>  <div class="scroll" :class="{show:isActive}">   <div id="toTop" @click="toTop(step)"><</div>   <div id="toBottom" @click="toBottom(step)">></div>  </div> </div></template><script> export default{  props:{   step:{ //此數據是控制動畫快慢的    type:Number,    default:50    }  },  data(){   return {    isActive:false,   }  },  methods:{   toTop(i){    //參數i表示間隔的幅度大小，以此來控制速度    document.documentElement.scrollTop-=i;    if (document.documentElement.scrollTop>0) {     var c=setTimeout(()=>this.toTop(i),16);    }else {     clearTimeout(c);    }   },   toBottom(i){    var clientHeight=document.documentElement.clientHeight||document.body.clientHeight;    var scrollHeight=document.documentElement.scrollHeight;    var height=scrollHeight-clientHeight; //超出窗口上界的值就是底部的scrolTop的值    document.documentElement.scrollTop+=i;    if (document.documentElement.scrollTop<height) {     var c=setTimeout(()=>this.toBottom(i),16);    }else {     clearTimeout(c);    }   }  },  created(){   var vm=this;   window.οnscrοll=function(){    if (document.documentElement.scrollTop>60) {     vm.isActive=true;    }else {     vm.isActive=false;    }   }  } }</script><style scoped> .scroll{   position: fixed;   right: 10px;   bottom: 60px;   width: 45px;   height: 90px;   cursor: pointer;   display: none;  }  .scroll>div{   width: 45px;   height: 45px;   transform: rotate(90deg);   line-height: 45px;   text-align: center;   font-size: 35px;   font-family: "黑體";   background-color: rgba(0,0,0,.2);   color: #fff;  }  .scroll>div:hover{   background-color: rgba(0,0,0,.5);  }  .show{   display: block;  }</style>