せいぜい速度の増加を最小限に抑えることは別として、これが常に希望どおりに動作するとは限らない可能性があります。
ソース:
:hiddenの決定方法は、jQuery1.3.2で変更されました。要素またはその親のいずれかがドキュメント内のスペースを消費しない場合、要素は非表示になっていると見なされます。CSSの可視性は考慮されていません(したがって
$(elem).css('visibility','hidden').is(':hidden') == false
)。
Checking for visibility is not incredibly complex, but IMHO even this excerpt shows it is not exactly trivial. While you could deal with the issue of making sure your visibility check works properly while using :hidden
every time you want to make sure this code is working correctly, you could just forget the 5 milliseconds that you might have a chance at saving and instead save yourself the time spent to understand the code and check the documentation every time there might be a problem with this area.
Just use plain old show()
; if there was a reason to do a check beforehand, I'm confident that the good ol' folks who make jQuery would have either provided a recommendation to do so in the docs somewhere or just hardcoded the check into the show
method/ :D