My statement: check if value on item class is empty , if empty set the value of sales order class ( if it has class set) in there.

var so_class = searchsalesorder[i].getValue({ name: "class", label: "Class" });
            var item = searchsalesorder[i].getValue({ name: "item", label: "Item" });
            var item_class = searchsalesorder[i].getValue({
                name: "class",
                join: "item",
                label: "Class"
            });

log those 3 things right after declaring them, should be pretty clear why/what isn't working

sure, thanks