How do I check if an element is hidden in jQuery?

this code might be more suitable:

// Checks css for display:[none|block], ignores visibility:[true|false]
$(element).is(":visible"); 

// The same works with hidden
$(element).is(":hidden"); 

Same as twernt's suggestion, but applied to a single element; and it matches the algorithm recommended in the jQuery FAQ

We use jQuery is() to check the selected element with another element, selector or any jQuery object. This method traverses along the DOM elements to find a match, which satisfies the passed parameter. It will return true if there is a match otherwise returns false.