The source code

    /**
     * @ignore
     *  Body for tab panels.
     * @author yiminghe@gmail.com
     */
    KISSY.add("tabs/body", function (S, Component) {

        return Component.Container.extend({

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

            bindUI: function () {
                this.on("afterSelectedPanelChange", function (e) {
                    if (e.newVal) {
                        if (e.prevVal) {
                            e.prevVal.set("selected", false);
                        }
                        e.newVal.set("selected", true);
                    }
                });
            }

        }, {
            ATTRS: {
                selectedPanel: {
                },
                allowTextSelection: {
                    value: true
                },
                focusable: {
                    value: false
                },
                handleMouseEvents: {
                    value: false
                },
                delegateChildren: {
                    value: false
                },
                defaultChildXClass: {
                    value: 'tabs-panel'
                }
            }
        }, {
            xclass: 'tabs-body'
        });

    }, {
        requires: ['component/base']
    });