如何使用Element Backtop回到顶部

<template>
 Scroll down to see the bottom-right button.
 <el-backtop target=".page-component__scroll .el-scrollbar__wrap"></el-backtop>
</template>

<template>
 Scroll down to see the bottom-right button.
 <el-backtop target=".page-component__scroll .el-scrollbar__wrap" :bottom="100">
  <div
   style="{
    height: 100%;
    width: 100%;
    background-color: #f2f5f6;
    box-shadow: 0 0 6px rgba(0,0,0, .12);
    text-align: center;
    line-height: 40px;
    color: #1989fa;
   }"
  >
   UP
  </div>
 </el-backtop>
</template>