Checking for postive length of jQuery wrapped set before calling methods on set

[Michael Matola]

I've come across some jQuery code that checks the length of the wrapped set before performing certain "getting rid of" methods, such as hide() or remove(). Presumably, the coder's intent is only to call hide() or remove() if there's actually something matched to hide or remove.

if ($("td:contains('something')").length > 0) {
  $("td:contains('something')").hide();
}

Elsewhere in the same code (presumably written by the same person, or team), there's no length check before other operations:

$("td:contains('somethingElse')").addClass("someClass");

Are such length checks necessary? If so, why?

[Bear Bibeault]

Not necessary. If there's nothing in the set, the methods will be a noop.

Building the wrapped set twice is also an unnecessary performance hit.

[Michael Matola]

Bear Bibeault wrote:Not necessary. If there's nothing in the set, the methods will be a noop.

That's what I was thinking. I wondered if it stemmed from a fear of calling a method on a null, but a set is returned, albeit empty.

Bear Bibeault wrote:Building the wrapped set twice is also an unnecessary performance hit.

Yes! In this example, I'm guessing the set is not a very expensive one to build, but in the general case, why would you do it twice.

Thanks for the confirmation.

Mike "off to fight crime" Matola

[Bear Bibeault]

Michael Matola wrote:Mike "off to fight crime" Matola

What color is your cape?

[Michael Matola]

Invisible.

[Bear Bibeault]

Ah, The Stealth Superhero.