When “UpdateBasketButton_OnClick” is called on Basket.aspx.cs, update each line item with either the new quantity. If the user clicks Remove, remove the order line in “RemoveOrderLineButton_OnClick”. Execute the basket pipeline so the order is kept up-to-date.
Continue the javascript gig from before by updating the basket using a code snippet similar to the one below. You need to collect the orderLineId and the Quantity entered from the basket table.