Fetching custom fields into a child table before save

Frappe Framework Custom Script
1

Here’s an example on how to fetch child table values before a document is saved. Works for values imported by code and manually updated. This particular Client Script example fetches the Customer Purchase Order number onto a custom column on the Production Plan:

frappe.ui.form.on('Production Plan', {
    setup(frm) {
        const sos = frm.get_field('sales_orders');
        // replace the refresh function
        sos.refresh_super = sos.refresh;
        sos.refresh = () => {
            sos.refresh_super();
            for (const row_name in sos.grid.grid_rows_by_docname) {
                frm.trigger('sales_order', 'Production Plan Sales Order', row_name);
            }
        }
    },
});

frappe.ui.form.on('Production Plan Sales Order', {
    sales_order(frm, cdt, cdn) {
        const row = locals[cdt][cdn];
        if (row.sales_order) {
            frappe.model.with_doc('Sales Order', row.sales_order, function () {
                const so = frappe.model.get_doc('Sales Order', row.sales_order);
                frappe.model.set_value(cdt, cdn, 'po_no', so.po_no);
            });
        }
    },
});