The source code

    /**
     * @ignore
     *  TabBar for KISSY.
     * @author yiminghe@gmail.com
     */
    KISSY.add("tabs/bar", function (S, Toolbar) {

        /**
         * @ignore
         */
        var TabBar = Toolbar.extend({

            createDom: function () {
                this.get("el").attr("role", "tablist");
            },

            handleKeyEventInternal: function (e) {
                var self = this;
                var current = self.get('selectedTab');
                var next = self.getNextItemByKeyEventInternal(e, current);
                if (S.isBoolean(next)) {
                    return next;
                } else {
                    next.set('selected', true);
                    return true;
                }
            },

            renderUI: function () {
                var bar = this,
                    children = bar.get("children");
                S.each(children, function (c) {
                    if (c.get("selected")) {
                        bar.set("selectedTab", c);
                    }
                });
            },

            _onSetSelectedTab: function (v, e) {
                var prev;
                if (v) {
                    if (e && (prev = e.prevVal)) {
                        prev.set("selected", false);
                    }
                    v.set("selected", true);
                }
            },

            _onSetHighlightedItem: function () {
                var self = this;
                TabBar.superclass._onSetHighlightedItem.apply(self, arguments);
                if (self.get('changeType') == 'mouse') {
                    self._onSetSelectedTab.apply(self, arguments);
                }
            },

            bindUI: function () {
                var self = this;
                self.on("afterSelectedChange", function (e) {
                    if (e.newVal && e.target.isTabsTab) {
                        self.set("selectedTab", e.target);
                    }
                });
            }

        }, {
            ATTRS: {
                selectedTab: {
                },
                changeType: {
                    value: "click"
                },
                defaultChildXClass: {
                    value: 'tabs-tab'
                }
            }
        }, {
            xclass: 'tabs-bar',
            priority: 30
        });

        /**
         * tabs change type
         * @enum {String}  KISSY.Tabs.ChangeType
         */
        TabBar.ChangeType = {
            /**
             * click
             */
            CLICK: "click",
            /**
             * mouse
             */
            MOUSE: "mouse"
        };

        return TabBar;

    }, {
        requires: ['toolbar']
    });