微信小程序实现点击返回顶层的方法

<scroll-view scroll-y style="height: 1000rpx;" scroll-top="50" enable-back-to-top="true" scroll-top="{{scrollTop.scroll_top}}" bindscroll="scrollTopFun">
<block wx:for="{{sortArr}}">
<template is="spL" data="{{item}}"></template>
</block>
</scroll-view> 
<!-- 联系客服 -->
<view class="findOur fliexBox"><contact-button type="default-light" size="15" session-from="weapp"></contact-button>客服</view>
<!-- 拨打电话 -->
<view class="callOur fliexBox" bindtap="call">电话</view>
<view class="fliexBox" style=" bottom: 150rpx; border: solid 1px green;" wx:if="{{scrollTop.goTop_show}}" catchtap="goTopFun">顶层</view>

var app = getApp();
Page({
data: {
hidden: true,
list: [],
scrollTop: {
scroll_top: 0,
goTop_show: false
},
scrollHeight: 0,
floorstatus:true,
sortArr:[
{
id: 1,
img: "../../images/2.jpg",
title: "君御豪园住宅",
introduction: "杭州不限购不限贷口住宅",
money: 5000,
vperson: 115,
tperson: 0
}
],
},
scrollTopFun: function (e) {
console.log(e.detail);
if (e.detail.scrollTop > 300) {//触发gotop的显示条件 
this.setData({
'scrollTop.goTop_show': true
});
} else {
this.setData({
'scrollTop.goTop_show': false
});
}
},
goTopFun: function (e) {
var _top = this.data.scrollTop.scroll_top;//发现设置scroll-top值不能和上一次的值一样，否则无效，所以这里加了个判断 
if (_top == 0) {
_top = 1;
} else {
_top = 0;
}
this.setData({
'scrollTop.scroll_top': _top
});
},
/**
* 生命周期函数--监听页面加载
*/
onLoad: function (options) {
var that = this;
wx.getSystemInfo({
success: function (res) {
that.setData({
scrollHeight: res.windowHeight
});
}
});
},

}）

.fliexBox{
width: 100rpx;
height: 50rpx;
background-color: #5db13b;
color: #ffffff;
text-align: center;
position: fixed;
right: 0rpx;
bottom: 85rpx;
border-radius: 20rpx 0rpx 0rpx 20rpx;
font-size: 26rpx;
line-height: 50rpx;
opacity: .6;
}
.callOur{
bottom: 20rpx;
}
contact-button{
opacity: 0;
position: absolute;
}