$.expr[":"].positionAbsolute = function(el){
	return $(el).css("position") === "absolute";
};

//Usage
alert($(":positionAbsolute").length); //alerts number elements positioned absolutley

//Or use a filter
$("div").filter(function(){return $(this).css('position') === 'absolute';});

$.expr[":"].positionAbsolute = function(el){
	return $(el).css("position") === "absolute";
};

//Usage
alert($(":positionAbsolute").length); //alerts number elements positioned absolutley

Example given in the book jQuery Enlightenment.

Create your own custom selectors in jQuery and manipulate as usual.

Custom jQuery selector

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