How to add a child table after creating a new document using frappe.new_doc() in JavaScript?

[NCP]

@How open new doc with all data in object

                    pr_item.item_code = po_item.item_code;
                    pr_item.qty = po_item.qty;
                    pr_item.rate = po_item.rate;

pr_item.item_code = "Item A";
pr_item.qty = 10;

try it.