JavaScript performance comparison Test case created by Sam Korn on 2011-4-14 Preparation code <div id='foo'>foo</div> <div id='bar'>bar</div><script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script> <script> var foo = $('#foo').hide(), bar = $('#bar'); $.fn.isVisible = function() { return $.expr.filters.visible(this[0]); }; </script> Preparation code output