AJAX Error when attempting to read xml file

Question

I'm trying to retrieve some data from an xml file using ajax

  <?xml version="1.0" encoding=UTF-8"?>

  <user>
     <u_idno>1</u_idno>
     <u_name>nobody</u_name>
     <u_srnm>nothing</u_srnm>
     <u_role>linux</u_role>
  </user>

  <user>
     <u_idno>2</u_idno>
     <u_name>yesbody</u_name>
     <u_srnm>something</u_srnm>
     <u_role>administrator</u_role>
  </user>

but I am getting an error

Uncaught TypeError: Cannot read property 'getElementsByTagName' of null

I am unsure why it would say null and I've been googling furiously to find out what I've done wrong but I'm clueless. My javascript is as followed

  function f_ajax() {

     var lv_request;

     try {
        lv_request = new XMLHttpRequest();
     } catch (error) {
        lv_request = new ActiveXObject("Microsoft.XMLHTTP");
     }

     lv_request.onreadystatechange = function() {

        if(lv_request.readyState == 4 && lv_request.status == 200) {

           lv_xml = lv_request.responseXML;
           lv_row = lv_xml.getElementsByTagName("user");
           lv_output = null;

           for (lv_cnt = 0; lv_cnt < lv_row.length; lv_cnt++) {

              lv_output = lv_output + lv_row[lv_cnt].childNodes[0].nodeValue;

           }

           document.getElementById("h2_ajax").innerHTML = lv_row;

        }

     }

     lv_request.open("GET", "data.xml", true);
     lv_request.send();

  };

  f_ajax();

If the value you are seeing in responseText is not fully-valid XML you will see a NULL in responseXML. — David Tansey
– David Tansey, Commented Jun 11, 2015 at 19:56
Take a look at the following post: stackoverflow.com/questions/3781387/responsexml-always-null -- in particular the answer that talks about parsing the responseText back to an XML document (i.e. the answer from Kenny). — David Tansey
– David Tansey, Commented Jun 11, 2015 at 19:59
Your opening <u_role> tag doesn't match the closing </role> tag. Is that a copying error or in the real file? — Barmar
– Barmar, Commented Jun 11, 2015 at 20:09

orcaman · Accepted Answer · 2015-06-11 20:07:14Z

1

Your XML is not well formed. It is missing a root and has some other issues. Try this:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <user>
   <u_idno>1</u_idno>
   <u_name>nobody</u_name>
   <u_srnm>nothing</u_srnm>
   <u_role>linux</u_role>
 </user>
 <user>
   <u_idno>2</u_idno>
   <u_name>yesbody</u_name>
   <u_srnm>something</u_srnm>
   <u_role>administrator</u_role>
 </user>
</root>

answered Jun 11, 2015 at 20:07

orcaman

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1 Comment

TheLovelySausage Over a year ago

Those incorrect closing tags were a typo in my question but it was the root tags that fixed it, I didn't know I needed a master parent, thanks so much

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