function something()
{
	var x = window.localStorage.getItem('aaa');

	x = x*1 + 1;

	window.localStorage.setItem('aaa', x);

	alert(x);
}


function add_to_cart(id)
{
	alert('You added pizza with id:' + id);
}

@@ -179,48 +179,141 @@
 %7B%0D%0A%09
-alert('You added pizza with id:' + id
+var key = 'product_' + id;%09%0D%0A%09%0D%0A%09var x = window.localStorage.getItem(key);%0D%0A%09x = x*1 + 1;%0D%0A%09window.localStorage.setItem(key, x
 );%0D%0A%7D%0D%0A
+%0D%0A%0D%0A

Update add_to_cart function + refactoring