The source code

    /**
     * @ignore
     *  Tabs render.
     * @author yiminghe@gmail.com
     */
    KISSY.add("tabs/render", function (S, Component) {
        var CLS = "tabs-top tabs-bottom tabs-left tabs-right";
        return Component.Render.extend({
            _onSetBarOrientation: function (v) {
                var self = this,
                    el = self.get("el");
                el.removeClass(self.getCssClassWithPrefix(CLS))
                    .addClass(self.getCssClassWithPrefix("tabs-" + v));
            }
        }, {
            ATTRS: {
                barOrientation: {
                    value: 'top'
                }
            },
            HTML_PARSER: {
                barOrientation: function (el) {
                    var orientation = el[0].className.match(/tabs-(top|bottom|left|right)\b/);
                    return orientation && orientation[1] || "top";
                }
            }
        });
    }, {
        requires: ['component/base']
    });