Comment by luckylion

Not having to worry whether some selector matches any elements is part of what makes jQuery attractive to many though. It's very "fire and forget", you send off your command to hide all .foo, and if there are any .foo they will be hidden, and if there are no .foo, nothing happens and you don't need to worry about it, much like CSS. If you write .foo { color: red; } and there isn't any .foo in the document it doesn't do anything but also has no negative side-effects (except that tiny overhead).