deferredRender : Boolean
True by default to defer the rendering of child items to the browsers DOM until a tab is activated. False will render all contained items as soon as the Ext.layout.container.Card is rendered. If there is a significant amount of content or a lot of heavy controls being rendered into panels that are not displayed by default, setting this to true might improve performance.
The deferredRender property is internally passed to the layout manager for TabPanels (Ext.layout.container.Card) as its Ext.layout.container.Card#deferredRender configuration value.
Note: leaving deferredRender as true means that the content within an unactivated tab will not be available.
Defaults to:true
기본적으로 True로 설정되어있고, Tabpanel의 자식(items)들이 해당 탭 선택 이전에 미리 렌더링 되지 않도록 설정합니다. False로 설정할 경우 모든 자식 탭의 아이템들을 페이지 초기화와 동시에 렌더링합니다. 연결되어있는 자식들이 많다면, 성능을 약간 향상시킬 수 있습니다.