Disable Item Sublist fields in User Event Script

Sample code for Disabling the item sublist fields in Before Load of User event Script

    const beforeLoad = (scriptContext) => {

        try {

            if (scriptContext.type == 'edit') {
                var record = scriptContext.newRecord;

               // fields that need to be disabled
                var itemFieldIds = ["quantity", "amount", "rate", "price"];
                var form = scriptContext.form;

                // Disable fields in SO
                for (var i = 0; i < itemFieldIds.length; i++) {
                    form.getSublist({

                        id: 'item'

                    }).getField({

                        id: itemFieldIds[i]

                    }).updateDisplayType({

                        displayType: serverWidget.FieldDisplayType.DISABLED

                    });
                }

            }
        } catch (e) {
            log.error("error @ beforeLoad", e);
        }
    }