This method tells you all information you need to know: whether one node is descendantof an ancestor of the other, whether it is before or after, and so on.
这个方法告诉您所有想知道的信息:一个节点是否是另一个节点的祖先的后代,它是在前面还是后面呢,等等。
2
If you must use descendant selectors, prefer child selectors, which at least only require evaluation of one additional node, not all the intermediate nodes up to an ancestor.