var evaluator = new XPathEvaluator(); 
//得到第一个div 
var result = evaluator.evaluate("//div", document.documentElement, null, 
         XPathResult.FIRST_ORDERED_NODE_TYPE, null); 
alert("First div ID is " + result.singleNodeValue.id); 

//get first div 
var result = document.evaluate("//div", document.documentElement, null, 
         XPathResult.FIRST_ORDERED_NODE_TYPE, null); 
alert("First div ID is " + result.singleNodeValue.id); 

//get all divs - iterator style 
var result = document.evaluate("//div", document.documentElement, null, 
         XPathResult.ORDERED_NODE_ITERATOR_TYPE, null); 
if (result){ 
  var node = result.iterateNext(); 
  while(node) { 
    alert(node.id); 
    node = node.iterateNext(); 
  } 
} 
//get all divs - SNAPSHOT style 
var result = document.evaluate("//div", document.documentElement, null, 
         XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null); 
if (result){ 
  for (var i=0, len=result.snapshotLength; i < len; i++) { 
    alert(result.snapshotItem(i).id); 
  } 
} 

function resolver(prefix){ 
  switch(prefix){ 
    case "wrox": return "http://www.wrox.com/"; 
    case "ncz": return "http://www.nczonline.net/"; 
    default: return "http://www.yahoo.com/"; 
  } 
} 

<books xmlns:wrox="http://www.wrox.com/" xmlns="http://www.amazon.com/"> 
  <wrox:book>Professional JavaScript</book> 
</books> 

var evaluator = new XPathEvaluator(); 
var resolver = evaluator.createNSResolver(xmldoc.documentElement); 

var evaluator = new XPathEvaluator(); 
var resolver = evaluator.createNSResolver(xmldoc.documentElement); 
var result = evaluator.evaluate("wrox:book", xmldoc.documentElement, 
         resolver, XPathResult.FIRST_ORDERED_NODE_TYPE, null); 
if (result){ 
  alert(result.singleNodeValue.firstChild.nodeValue); 
} 

function createDocument(){ 
  if (typeof arguments.callee.activeXString != "string"){ 
    var versions = ["MSXML2.DOMDocument.6.0", 
            "MSXML2.DOMDocument.3.0", 
            "MSXML2.DOMDocument"]; 
    for (var i=0,len=versions.length; i < len; i++){ 
      try { 
        var xmldom = new ActiveXObject(versions[i]); 
        arguments.callee.activeXString = versions[i]; 
        return xmldom; 
      } catch (ex){ 
        //skip 
      } 
    } 
  } 
  return new ActiveXObject(arguments.callee.activeXString); 
} 

var xmldoc = createDocument(); 
xmldoc.loadXML(""); 

var xhr = new XMLHttpRequest(), 
  xmldoc; 
xhr.open("get", "data.xml", true); 
xhr.onreadystatechange = function(){ 
  if (xhr.readyState == 4){ 
    if (xhr.status >= 200 && xhr.status < 300){ 
      xmldoc = xhr.responseXML; 
    } 
}; 
xhr.send(null); 

<xml id="myXML" src="data.xml"></xml>

var xmldoc = document.getElementById("myXML").XMLDocument;

<books xmlns:wrox="http://www.wrox.com/" xmlns="http://www.amazon.com/">
  <wrox:book>Professional JavaScript</book>

xmldoc.setProperty("SelectionNamespaces",
  "xmlns:wrox='http://www.wrox.com/' xmlns='http://www.amazon.com/'");
var book = xmldoc.documentElement.selectSingleNode("wrox:book");