Copy field values from one child table to another child table on the same doctype

hi i am new to erpnext, is there any way to copy the field (Item Code and Item Name) on items to field (Item Code and Item Name) on Item tax breakdown.

i Tried using something like this but to no avail

> frappe.ui.form.on("Quotation", "items", function(frm) {
>     frappe.model.with_doc("Quotation", frm.doc.items, function() {
>         var tabletransfer= frappe.model.get_doc("Quotation", frm.doc.items)
>         $.each(tabletransfer.items, function(index, row){
>             d = frm.add_child("item_tax_breakdown");
>             d.item_code = row.item_code;
>             d.item_name = row.item_name;
>             frm.refresh_field("item_tax_breakdown");
>         });
>     })
> });