jquery input "array key" selector

jq_inputkey_selector.js

/*
 The past few days, I've seen people in #jquery asking about using selectors
 to match inputs with names that would produce arrays on the backend, such as
 
 <input name="foo[]" />
 <input name="foo[foo]" />
 <input name="foo[bar][baz]" />
 
 So I wrote a selector that works with these.
 Feel free to use/improve
 
 A demo is up at:
 http://bbby.org/share/jquery_key_selector.php
*/

jQuery.extend(jQuery.expr[':'],{
	key:function(elm,i,filter)
	{
		if(typeof elm.name == undefined)
			return false;
		
		var qual = filter[3],
			name = elm.name;
		
		if(!name.match(/\[.*\]/))
			return false;
		if(qual == undefined)
			return true;
		
		var keys=qual.split(/,/g),
			l=keys.length;
		
		while(l--)
			keys[l] = "\\["+(keys[l].replace(/^\s+|\s+$/g,''))+"\\]";
		
		return name.match(new RegExp(keys.join('')));
	}
});

i want to see a demo. Thanks!