how to check if an item exist in sessionstorage?

[rUmmeh]

I am creating a web page where the user can add an item into a dropbox buy clicking a button. The sessionstorage store the partnum and quantity of the item. The dropbox will display the details (quantity would be 1)of the item selected. How do I update the quantity to 2 if the same item is selected?\[code\] $("#btnBuy0").click(function() { $("#dropbox").append('<span><img class = "thumb" src="http://stackoverflow.com/questions/images/21_metoyou.jpg" />' + teddy[0].desc + ", Price