Using jQuery, how would you test if an element #el

Using jQuery, how would you test if an element #elem is visible or hidden?

$('#elem').is('visible');
$('#elem:hidden');
$('#elem').attr('visible');
$('#elem').is(':hidden');

Explanation

$('#elem').is('visible'); - wrong syntax; $('#elem:hidden'); - only select hidden elements; $('#elem').attr('visible'); - wrong attribute; $('#elem').is(':hidden'); - correct way, according to jQuery refference; The is() method checks if one of the selected elements matches the selectorElement.