Newsletter popup with session storage

newsletter-popup.js

  if (typeof(Storage) !== "undefined") {
        // Store
        function showPopup(){
	        window.setTimeout(function () {
            	$('#newsletter-modal').modal('show');
                sessionStorage.setItem("popup", 'hide');         
	        },6000); 
        }	
        if( !sessionStorage.getItem("popup")){
        	sessionStorage.setItem("popup", 'show');         
        }
        if( sessionStorage.getItem("popup") == 'show'){
        	showPopup();
        }
    }