运用AJAX技术解析XML文件

      这是数周前写的一个关于javascript程序了。”温故而知新”今天拿出来，温习温习，加深印象！其中三段关于AJAX的代码可以说是通用代码。

var xmlhttp;

//根据判断的浏览器的不同类型创建XMLHttpRequest对象
function createXMLHttpRequest(){
    if (window.ActiveXObject) {
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    else
        if (window.XMLHttpRequest) {
            xmlhttp = new XMLHttpRequest();
        }
}

//发起异步请求
function startAsyRequest(){
    createXMLHttpRequest();//调用createXMLHttpRequest()XMLHttpRequest对象
    xmlhttp.onreadystatechange = handleStateChange;
    xmlhttp.open("GET", "bbc.xml?timespan=" + new Date().getTime(), true);
    xmlhttp.send(null);
}

//XMLHttpRequest对象的readystate值变化时的处理函数
function handleStateChange(){
    if (xmlhttp.readyState == 4) {
        if (xmlhttp.status == 200) {
            bbcAnalyze();//调用解析请求的XML文件的函数
        }
        else {
            alert("请检查web服务器是否运行正常！");
        }
    }
}

//解析(利用XML DOM)请求的XML文件并利用HTML DOM以表格形式呈现数据
function bbcAnalyze(){

    xmlDoc = xmlhttp.responseXML;
   var table1 = document.getElementById("tb1");

    //alert(xmlDoc);
    if (xmlDoc) {
        var countryNodes = xmlDoc.getElementsByTagName("Country");
        //alert(countryNodes.length);
        for (var i = 0; i < countryNodes.length; i++) {
            var t1=document.createElement("tr");
            var region = countryNodes[i].getAttribute("Region");
            var td1 = document.createElement("td");
            var newpnode1 = document.createTextNode(region);
            td1.appendChild(newpnode1);
            t1.appendChild(td1);
            var name = xmlDoc.getElementsByTagName("Name")[i].childNodes[0].nodeValue;
            var td2 = document.createElement("td");
            var newpnode2 = document.createTextNode(name);
            td2.appendChild(newpnode2);
            t1.appendChild(td2);
            var area = xmlDoc.getElementsByTagName("Area")[i].childNodes[0].nodeValue;
            var td3 = document.createElement("td");
            var newpnode3 = document.createTextNode(area);
            td3.appendChild(newpnode3);
            t1.appendChild(td3);
            var population = xmlDoc.getElementsByTagName("Population")[i].childNodes[0].nodeValue;
            var td4 = document.createElement("td");
            var newpnode4 = document.createTextNode(population);
            td4.appendChild(newpnode4);
            t1.appendChild(td4);
            if (xmlDoc.getElementsByTagName("GDP")[i].hasChildNodes()) {
                var gdp = xmlDoc.getElementsByTagName("GDP")[i].childNodes[0].nodeValue;
                var newpnode5 = document.createTextNode(gdp);
                td5 = document.createElement("td");
                td5.appendChild(newpnode5);
                t1.appendChild(td5);
            }
            else {
                gdp = "";
                td6 = document.createElement("td");
                var newpnode6 = document.createTextNode(gdp);
                td6.appendChild(newpnode6);
                t1.appendChild(td6);
            }
            table1.appendChild(t1);
            //alert(table1);
        }
    }
    else {
        alert("xmlDoc文件为空,操作失败！");
    }
}