Using JavaScript to parse an XML file

I am new to Stack OverFlow and coding in general. I am trying to take an XML file and render it in the browser using JavaScript. I have looked around at some sample code of how to do this and came up with the following code:

<!DOCTYPE html>
<html>
<body>

<script>
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
  xmlhttp.open("GET","social.xml",false);
  xmlhttp.send();
  xmlDoc=xmlhttp.responseXML; 

document.write("<table border='1'>");
var x=xmlDoc.getElementsByTagName("CD");
for (i=0;i<x.length;i++)
  { 
  document.write("<tr><td>");
  document.write(x[i].getElementsByTagName("c_id")[0].childNodes[0].nodeValue);
  document.write("</td><td>");
  document.write(x[i].getElementsByTagName("facebook_id")[0].childNodes[0].nodeValue);
  document.write("</td></tr>");
  }
  document.write("</table>");
</script>

</body>
</html>

Anyway, when I run this on my local server none of the data that I am trying to display in the table appears. My .html file and .xml file are in the same folder, so I believe I have the correct file pathway. I could just be making a rookie mistake here, but I can't for the life of me figure out why a table listing the c_id and facebook_id values is not being created. I looked around for answers and haven't been able to find any. Any help would be greatly appreciated. Thanks!

Answers:

Answer

You need to add an onload event listener to the xmlhttprequest before sending the request. Also, you might need to parse the XML with a DOMParser. Anyway, this should work on modern browsers:

<!DOCTYPE html>
<html>
    <body>

        <script>
            if (window.XMLHttpRequest)
            {// code for IE7+, Firefox, Chrome, Opera, Safari
                xmlhttp=new XMLHttpRequest();
            }
            else
            {// code for IE6, IE5
                xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
            }



            xmlhttp.onload = function() {
                var xmlDoc = new DOMParser().parseFromString(xmlhttp.responseText,'text/xml');

                console.log(xmlDoc);

                document.write("<table border='1'>");
                var x=xmlDoc.getElementsByTagName("CD");
                for (i=0;i<x.length;i++)
                { 
                    document.write("<tr><td>");
                    document.write(x[i].getElementsByTagName("c_id")[0].childNodes[0].nodeValue);
                    document.write("</td><td>");
                    document.write(x[i].getElementsByTagName("facebook_id")[0].childNodes[0].nodeValue);
                    document.write("</td></tr>");
                }
                document.write("</table>");

            }


            xmlhttp.open("GET","social.xml",false);
            xmlhttp.send();
            </script>

    </body>
</html>

Now, just a couple of things worth mentioning about what you're doing:

  • xmlhttprequest objects have many different parameters that mean a variety of things: readystate, status code, the works. You might benefit looking a bit more into those.

  • document.write should really never be used, ever. In fact, any means of HTML injection should be handled very carefully. You could use a template-based solution common in many MVC-esque frameworks, or mine if you want :)

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