怎样用JS生成这样的XML文档????

var xmlObj = new ActiveXObject("MSXML2.DOMDocument");
xmlObj.loadXML("<?xml version=\"1.0\"?><Dataset/>");
var root = xmlObj.documentElement;
var p = xmlObj.createElement("p");
p.setAttribute("typeid","0000100001");
p.setAttribute("usercode","01001");
p.setAttribute("qty","10");
p.setAttribute("price","10");
root.appendChild(p);
root.appendChild(p);
root.appendChild(p);