parentElement is new to Firefox 9 and to DOM4, but it has been present in all other major browsers for ages.
(parentElement是Firefox 9和DOM4的新功能，但它已经存在于所有其他主流浏览器中。)
In most cases, it is the same as parentNode .
(在大多数情况下，它与parentNode相同。)
The only difference comes when a node's parentNode is not an element.(唯一的区别在于节点的parentNode不是元素。)
If so, parentElement is null .(如果是，则parentElement为null 。)
As an example:
(举个例子：)
document.body.parentNode; // the <html> element
document.body.parentElement; // the <html> element
document.documentElement.parentNode; // the document node
document.documentElement.parentElement; // null
(document.documentElement.parentNode === document); // true
(document.documentElement.parentElement === document); // false
Since the <html> element ( document.documentElement ) doesn't have a parent that is an element, parentElement is null .
(由于<html>元素（ document.documentElement ）没有父元素，因此parentElement为null 。)
(There are other, more unlikely, cases where parentElement could be null , but you'll probably never come across them.)(（还有其他更不可能的情况，其中parentElement可能为null ，但您可能永远不会遇到它们。）)
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