效果预览：
js部分：
Page({ data: { topNum: 0 }, returnTop: function () { this.setData({ topNum: this.data.topNum = 0 }); }}) wxml部分：
<scroll-view scroll-y scroll-with-animation='true' scroll-top='{{ topNum }}'> <view>1</view> <view>1</view> <view>1</view> <view>1</view> <view>1</view> <view>1</view> <view>1</view> <view>1</view> <view>1</view> <view>1</view></scroll-view><view class='top' catchtap='returnTop'>顶部</view>wxss部分:
page{ width: 100%; height: 100%;}scroll-view{ height: 100%; width: 100%;}view{ width: 100%; height: 200px; text-align: center; line-height: 200px; font-weight: 600;}view:nth-child(odd){ background-color: red;}.top{ width: 50px; height: 50px; position: fixed; right: 10px; bottom: 10px; z-index: 1; background-color: yellow; color: red; text-align: center; line-height: 50px;}
