Add a new item line in the record

if(scriptContext.type==scriptContext.UserEventType.CREATE) {

                           var recId = scriptContext.newRecord.id;
                           log.debug("id", recId)
                           var Record = record.load({
                               type: record.Type.INVOICE,
                               id: recId,
                               isDynamic: true
                           });
                           Record.selectNewLine({
                                   sublistId: 'item'
                               });

                               Record.setCurrentSublistValue({
                                   sublistId: 'item',
                                   fieldId: 'item',
                                   value: 887619,

                               });
                               Record.setCurrentSublistValue({
                                   sublistId: 'item',
                                   fieldId: 'quantity',
                                   value: '1'
                               });

                               Record.setCurrentSublistValue({
                                   sublistId: 'item',
                                   fieldId: 'rate',
                                   value: tax
                               });
                               var taxDisply= Record.setCurrentSublistValue({
                                   sublistId: 'item',
                                   fieldId:'taxcode_display',
                                   value: -22
                               })
                               log.debug("taxDisply",taxDisply);
                               Record.commitLine({
                                   sublistId: 'item'
                               });

                               Record.save();

}