how to check display none or not in jquery code example

Example 1: jquery display none

The correct way to do this is to use show and hide:

$('#id').hide();
$('#id').show();

An alternate way is to use the jQuery css method:

$("#id").css("display", "none");
$("#id").css("display", "block");

Example 2: how to check if div is display none jquery

if(!$('#yourID').is(':visible'))
{

}