$.fn.is() could be enhanced to check existence.

[andy@…]

$.fn.is() could be modified slightly to check the existence of the selector parameter. If no parameters are present, it could return this.length > 0 as a nice short-hand.

E.g.

var form = $('form');
if(!form.find(':input.dirty').is())
   return;
$.post(form.attr('action'), form.serialize());

A common jQuery newb error is to check a jQuery object for truthiness; of course this fails because an empty jQuery object still exists. $.fn.is() though could could be a quick, easy, and valuable shortcut.

See a duck-punched version in action here:  http://jsfiddle.net/bReG4/

[sindresorhus]

You can already do this with the .length property.

"if( !form.find(':input.dirty').length )"

[Andy Edinborough <andy@…>]

Yes, I know you can. :] I was only offering this as an explicit method that didn't rely on the implicit nature of truthiness.