借助CSS Shapes实现元素滚动自动环绕iPhone X的刘海

CSS代码：
.box {
    max-width: 414px;
    height: 480px;
    border: solid #000;
    margin: auto;
    overflow: auto;
}
.shape {
    float: left;
    width: 30px; height: 340px;
    shape-outside: polygon(0 0, 0 150px, 16px 154px, 30px 166px, 30px 314px, 16px 326px, 0 330px, 0 0);
    transition: shape-outside .15s;
}
.liuhai {
    width: 24px; height: 180px;
    background: url(liu.png) no-repeat left center;
    position: absolute;
    margin-top: 150px;
}
.content ul {
    list-style: none;
    padding: 0;
    margin: 0;
}
.content li {
    border-bottom: 1px solid #eee;
    padding: .5em;
}
HTML代码：
<div id="box" class="box">
    <i id="shape" class="shape"></i>
    <i class="liuhai"></i>
    <div class="content">
        <ul>
            <li>为了防止看花眼</li>
            <li>我就手动敲下面的文字</li>
            <li>原本我偷懒</li>
            ...
            <li>理论上还可以使用CSS region实现</li>
            <li>但没有这个方法容易理解</li>
        </ul>
    </div>
</div>
JS代码：
var eleShape = document.getElementById('shape');
var eleBox = document.getElementById('box');
// 保证shape元素高度足够
eleShape.style.height = eleBox.scrollHeight + 'px';

var funShape = function () {
    var scrollTop = eleBox.scrollTop;
    // 滚动偏移应用在shape-outside上
    var shapeOutside = 'polygon(0 0, 0 '+ (150 + scrollTop) +'px, 16px '+ (154 + scrollTop) +'px, 30px '+ (166 + scrollTop) +'px, 30px '+ (314 + scrollTop) +'px, 16px '+ (326 + scrollTop) +'px, 0 '+ (330 + scrollTop) +'px, 0 0)';
    eleShape.style.shapeOutside = shapeOutside;
};
// 滚动时候实时改变shape形状
eleBox.addEventListener('scroll', funShape);
funShape();