显示了服务器向浏览器返回的XML文档的内容

在浏览器上会生成具有两个按钮的 HTML 页面。点击第一个按钮，将从服务器加载 XML 文档，然后在警告框中显示列于文档中的所有州。点击第二个按钮也会从服务器加载 XML 文档，不过只在警告框中显示北部地区的各个州。
ParseXML.htm完整代码：

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >
< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head >
     < title > Parsing XML Responses with the W3C DOM </ title >
< script  type ="text/javascript" >
var xmlHttp;
var requestType = "";

function createXMLHttpRequest() {
    if (window.ActiveXObject) {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } 
    else if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    }
}
    
function startRequest(requestedList) {
    requestType = requestedList;
    createXMLHttpRequest();
    xmlHttp.onreadystatechange = handleStateChange;
    xmlHttp.open("GET", "parseXML.xml", true);
    xmlHttp.send(null);
}
    
function handleStateChange() {
    if(xmlHttp.readyState == 4) {
        if(xmlHttp.status == 200) {
            if(requestType == "north") {
                listNorthStates();
            }
            else if(requestType == "all") {
                listAllStates();
            }
        }
    }
}
 
function listNorthStates() {
    var xmlDoc = xmlHttp.responseXML;
    var northNode = xmlDoc.getElementsByTagName("north")[0];
    
    var out = "Northern States";
    var northStates = northNode.getElementsByTagName("state");
    
    outputList("Northern States", northStates);
}

function listAllStates() {
    var xmlDoc = xmlHttp.responseXML;
    var allStates = xmlDoc.getElementsByTagName("state");
    
    outputList("All States in Document", allStates);
}

function outputList(title, states) {
    var out = title;
    var currentState = null;
    for(var i = 0; i < states.length; i++) {
        currentState = states[i];
        out = out + "/n- " + currentState.childNodes[0].nodeValue;
    }
    
    alert(out);
}
</ script >
</ head >

< body >
     < h1 > Process XML Document of U.S. States </ h1 >
     < br />< br />
     < form  action ="#" >
         < input  type ="button"  value ="View All Listed States"  onclick ="startRequest('all');" />
         < br />< br />
         < input  type ="button"  value ="View All Listed Northern States"  onclick ="startRequest('north');" />
     </ form >
</ body >
</ html >

ParseXML.xml内容：

<? xml version="1.0" encoding="UTF-8" ?>
< states >
   < north >
     < state > Minnesota </ state >
     < state > Iowa </ state >
     < state > North Dakota </ state >
   </ north >
   < south >
     < state > Texas </ state >
     < state > Oklahoma </ state >
     < state > Louisiana </ state >
   </ south >
   < east >
     < state > New York </ state >
     < state > North Carolina </ state >
     < state > Massachusetts </ state >
   </ east >
   < west >
     < state > California </ state >
     < state > Oregon </ state >
     < state > Nevada </ state >
   </ west >
</ states >