Ext.require的作用

        Ext.require([

    'Ext.tab.*'

]);

Ext.require这个的作用是什么，百度了一下好像说是只加载需要的组件....这是什么意思，是只加在Ext.tab.js这个文件？




还有 为什么ext-4.1.1a ext-4.0.7-gpl这两个版本创建window的速度特别慢？

win = Ext.create('widget.window', {

                    title: 'Layout Window',

                    closable: true,

                    closeAction: 'hide',

                    width: 600,

                    minWidth: 350,

                    height: 350,

                    layout: 'border',

                    bodyStyle: 'padding: 5px;',

                    items: [{

                        region: 'west',

                        title: 'Navigation',

                        width: 200,

                        split: true,

                        collapsible: true,

                        floatable: false

                    }, {

                        region: 'center',

                        xtype: 'tabpanel',

                        items: [{

                            title: 'Bogus Tab',

                            html: 'Hello world 1'