.contains() 判断一个元素内是否包含另一个元素

<div id="parent">
  parent
  <div id="children">children</div>
</div>

js代码：

let parent = document.getElementById('parent')
let children = document.getElementById('children')
if (parent.contains(children)) {
  console.log(true)
}
if (children.contains(parent)) {
  console.log(false)
}

结果返回true