IntersectionObserver.relativeToViewport

解釋：指定頁(yè)面顯示區(qū)域作為參照區(qū)域之一

方法參數(shù)

Object object

margins 參數(shù)說(shuō)明: 用來(lái)擴(kuò)展（或收縮）參照節(jié)點(diǎn)布局區(qū)域的邊界。

示例 

在開發(fā)者工具中打開

圖片示例

代碼示例

<view class="wrap">
    <scroll-view class="scroll-view" scroll-y>
        <view class="scroll-area" style="{{appear ? 'background: #ccc' : ''}}">
            <text class="notice">向下滾動(dòng)讓小球出現(xiàn)</text>
            <!-- 占位元素 -->
            <view class="filling"></view> 
            <!-- 小球 -->
            <view class="ball"></view>
        </view>
    </scroll-view>
</view>

Page({
    onReady() {
        this.intersectionObserver = swan.createIntersectionObserver(this);
        this.intersectionObserver
            .relativeToViewport({
                bottom: 100
            });
        console.log('實(shí)例：', this.intersectionObserver); // {selector: null, margins: {bottom: 100}} 用來(lái)收縮參照區(qū)域
        swan.showModal({
            title: 'relativeToViewport',
            content: JSON.stringify(this.intersectionObserver._relativeInfo)
        });
    },
    onUnload() {
        this.intersectionObserver && this.intersectionObserver.disconnect();
    }
});