add delay for keypress event in extjs

{
                            xtype: 'textfield',
                            itemId: 'description',
                            fieldLabel: 'Description',
                            enableKeyEvents: true,
                            listeners: {
                                keyup: {
                                    fn: me.onDescriptionKeyup,
                                    buffer: 500,
                                    scope: me
                                }
                            }
                        },