Javascript OpenLayers.Request.Post中没有XMLDocument

我使用异步OpenLayers POST请求并通过responseText获取以下字符串：

<?xml version="1.0" encoding="UTF-8"?>
<gml:TimePeriod xmlns:gml="http://www.opengis.net/gml">
 <gml:beginPosition>2011-10-18T15:15:00.000+02:00</gml:beginPosition>
<gml:endPosition>2014-11-23T14:45:00.000+01:00</gml:endPosition>
</gml:TimePeriod>

//xml回调处理程序

function handler(request) {
                     var xmlText = request.responseText;    
                     console.log(xmlText); //returns the string above

                     var xmlDoc = request.responseXML;
                     console.log(xmlDoc);   // returns the empty XMLDocument    

                    var timeArray = xmlDoc.getElementsByTagName('TimePeriod');        
                    console.log("timeArray:",timeArray);

                  }; 

//创建XML文档

 function CreateXMLDocument () {
    var xmlDoc = request.responseText;
        if (window.DOMParser) {
            var parser = new DOMParser();
            xmlDoc = parser.parseFromString (xmlDoc, "text/xml");
        } else if (window.ActiveXObject) {
            xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
            xmlDoc.async = false;
            xmlDoc.loadXML (xmlDoc);
        }

        var TimeNode = xmlDoc.getElementsByTagName ("TimePeriod");
        var beginPosition = TimeNode.getAttribute ("beginPosition");
        alert ("The Timeperiod is " + beginPosition);
  }

你知道如何将“TimePeriod”标记放入对象“timeArray”中吗？ 为什么请求对该字符串输出有效而对XMLDocument无效？

我已经弄明白了！ 通过更改几行代码，我在警报中收到了请求的时间段。 我交换了XML警报处理程序代码，没有使用XML回调处理程序

//xml警报处理程序

                  function handler(request) {
                    var xmlStr = request.responseText;  
                    console.log("xmlStr:",xmlStr);      

                    var parser=new DOMParser();
                    var xmlDoc=parser.parseFromString(request.responseText,"text/xml");
                    var gml = xmlDoc.getElementsByTagName("gml:beginPosition")[0].firstChild.data;  
                    console.log("gml:beginPosition", gml);
                    alert(gml);
                  }; 

                  function handler(request) {
                    var xmlStr = request.responseText;  
                    console.log("xmlStr:",xmlStr);      

                    var parser=new DOMParser();
                    var xmlDoc=parser.parseFromString(request.responseText,"text/xml");
                    var gml = xmlDoc.getElementsByTagName("gml:beginPosition")[0].firstChild.data;  
                    console.log("gml:beginPosition", gml);
                    alert(gml);
                  };