if( $("#selector").css('display') == 'block') {
//Your code
}
// select your element
var elem = jQuery('#elem');
// check the display property (just 1 example)
if (elem.css('display') != 'none')
{
console.log('elem display is NOT none')
}
else
{
console.log('elem display IS none')
}
// I hope that this helps! Happy coding :)