jquery onscreen / offscreen selector

gistfile1.js

$.expr[':'].onscreen = function(obj){
	var $win = $(window), pos = $(obj).position();
	return $.contains(document.documentElement, obj) && pos.top < $win.height() && pos.left < $win.width();
};

$.expr[':'].offscreen = function(obj){
	return !$(obj).is(':onscreen');
};

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