The source code

    /*!
     * Ext JS Library 3.2.1
     * Copyright(c) 2006-2010 Ext JS, Inc.
     * licensing@extjs.com
     * http://www.extjs.com/license
     */
    Ext.ns('Ext.ux');

    Ext.ux.Tabs = Ext.extend(Ext.util.Observable, {
    	// Configuration options
        activeTab: 0,

    	// Our class constructor
        constructor : function(element, config) {
            Ext.apply(this, config);
            Ext.ux.Tabs.superclass.constructor.call(this);

            this.addEvents(
                'beforetabchange',
                'tabchange'
            );

            this.el = Ext.get(element);
            this.init();
        },

        init : function() {
            var me = this;

    		this.el.addClass('ux-tabs-container');

    		this.tabStrip = this.el.child('ul');
    		this.tabStrip.addClass('ux-tabs-strip');

    		this.tabStrip.on('click', this.onStripClick, this, {delegate: 'a'});

    		this.tabs = this.tabStrip.select('> li');
    		this.cards = this.el.select('> div');

    		this.cardsContainer = this.el.createChild({
    			cls: 'ux-tabs-cards'
    		});
    		this.cardsContainer.setWidth(this.el.getWidth());

    		this.cards.addClass('ux-tabs-card');
    		this.cards.appendTo(this.cardsContainer);

    		this.el.createChild({
    			cls: 'ux-tabs-clearfix'
    		});

    		this.setActiveTab(this.activeTab || 0);
    	},

    	onStripClick : function(ev, t) {
    		if(t && t.href && t.href.indexOf('#')) {
    			ev.preventDefault();
    			this.setActiveTab(t.href.split('#')[1]);
    		}
    	},

    	setActiveTab : function(tab) {
    		var card;
    		if(Ext.isString(tab)) {
    			card = Ext.get(tab);
    			tab = this.tabStrip.child('a[href=#' + tab + ']').parent();
    		}
    		else if (Ext.isNumber(tab)) {
    			tab = this.tabs.item(tab);
    			card = Ext.get(tab.first().dom.href.split('#')[1]);
    		}

    		if(tab && card && this.fireEvent('beforetabchange', tab, card) !== false) {
    			card.radioClass('ux-tabs-card-active');
    			tab.radioClass('ux-tabs-tab-active');
    			this.fireEvent('tabchange', tab, card);
    		}
    	}
    });