ajax回到xml根节点

ajax返回xml根节点

function _getAjaxDocumentRoot(xmlHttpRequest){
?var root = null;
?if (xmlHttpRequest.responseText.length == 4)
??return null;
?if (xmlHttpRequest.responseXML.xml == "" && xmlHttpRequest.responseText != ""){
??try {
???var doc = new ActiveXObject ("Microsoft.XMLDOM");
???var xmlText = Start.Util.decodeText(xmlHttpRequest.responseText);
???doc.loadXML (xmlText);
???root = doc.documentElement;???
??} catch (e) {
???root = null;
??}
?}else{
??try {
???root = xmlHttpRequest.responseXML.documentElement;
??} catch (e) {
???root = null;
??}
?}?
?return root;
}