小程序IntersectionObserver用法

this._observer = wx.createIntersectionObserver(this);
this._observer.relativeTo('.jump-list').observe('.course-info', res => {
  this.setData({
    appear: res.intersectionRatio > 0
  });
});

<view class="sticky-menu" hidden="{{appear}}">
    <view class="item-box">
        <text class="item {{toView=='chapter'?'active':''}}" bindtap="jumpTo" data-optg="chapter">章节</text>
        <text class="item {{toView=='teacher'?'active':''}}" bindtap="jumpTo" data-optg="teacher">教师</text>
        <text class="item {{toView=='school'?'active':''}}" bindtap="jumpTo" data-optg="school">学校</text>
        <text class="item {{toView=='courses'?'active':''}}" bindtap="jumpTo" data-optg="courses">推荐</text>
    </view>
</view>

<scroll-view class="jump-list" style="height: {{scrollViewHeight*2}}rpx"
    scroll-into-view="{{toView}}" 
    scroll-y="true" 
    scroll-with-animation="true">

    <view class="course-info">
        <view class="course-tag">{{course_info.grade_name}} {{course_info.course_name}}</view>
        <view class="title">{{course_info.curriculum_name}}</view>
        <view class="info flex">
            <view class="study-num">
                已有{{course_info.buy_num}}人学习
                <text class="limited">限量{{course_info.max_num}}人</text>
            </view>
            <view wx:if="{{course_info.now_cost!=undefined}}" class="price">{{course_info.now_cost==0?'免费':'￥'+course_info.now_cost}}</view>
        </view>
    </view>
</scroll-view>