var x = $(

        "<xml><products><product id=\"P1\">AA</product>" +

        "<product id=\"P2\">BB</product>" +

        "<product id=\"P3\">CC<part>X</part></product></products></xml>");

    alert(x.find("products product").size());

    alert(x.find("product:eq(1)").attr("id"));

    alert(x.find("product").eq(2).find("part").text());

    alert(x.find("product[@id='P1']").text());