MatanyaAnsuman Bebarta提出了一个问题：Difference between $('#tabs a') and $('#tabs').find('a')，或许与您遇到的问题类似。
$("#tabs a") evaluates from right to left - which is the native direction of both Sizzle selector engine and
querySelectorAll - i.e. first it finds all of the anchor elements in the page and then narrows it down to those under
$("#tabs").find("a") evaluates - more intuitively - from left to right, i.e. first it finds
#tabs, and then only the anchor elements under it.
Clearly the latter would yield better performance, but it would only be noticeable accumulatively; that is, if you run thousands of queries. Otherwise, the difference is negligible.