You can use :visible for visible elements and :hidden to find out hidden elements. This hidden elements have display attribute set to none.
hiddenElements = $(':hidden');
visibleElements = $(':visible');
To check particular element.
if($('#yourID:visible').length == 0)
{
}
Elements are considered visible if they consume space in the document.
Visible elements have a width or height that is greater than zero,
Reference
You can also use is() with :visible
if(!$('#yourID').is(':visible'))
{
}
If you want to check value of display then you can use css()
if($('#yourID').css('display') == 'none')
{
}
If you are using display the following values display can have.
display: none
display: inline
display: block
display: list-item
display: inline-block
Check complete list of possible display values here.
To check the display property with JavaScript
var isVisible = document.getElementById("yourID").style.display == "block";
var isHidden = document.getElementById("yourID").style.display == "none";