Can't parse a tag from xml using ajax on a table

The question is : How can I do this table call using ajax. Only display the values when a tag "code" is with a value "10 222" the xml is

<?xml version='1.0' encoding='utf-8' ?>
<?xml-stylesheet type='text/xsl' href='thefile.xsl' ?>

<inv100 xmlns:xsi='http://ift.tt/1pu4Cto'  
xsi:noNamespaceSchemaLocation='archivo.xsd'>
<tab_inv>
<Descripcion> Food for dog </Descripcion>
<precio> 6.55 </precio>
<code> 01 22 </code>
</tab_inv>
<tab_inv>
<Descripcion> Food for cat </Descripcion>
<precio> 8.55 </precio>
<code> 10 222 </code>
</tab_inv>
<tab_inv>
<Descripcion> Food for dragons </Descripcion>
<precio> 122.55 </precio>
<code> 14 2212 </code>
</tab_inv>
</inv100>

And this is the script

<script>
function loadXMLDoc() {
  var xmlhttp = new XMLHttpRequest();
  xmlhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      myFunction(this);
    }
  };
  xmlhttp.open("GET", "thefile.xml", true);
  xmlhttp.send();
}
function myFunction(xml) {
  var i;
  var xmlDoc = xml.responseXML;
  var table="<tr><th>Descripcion</th><th>Precio</th></tr>";
  var x = xmlDoc.getElementsByTagName("tab_inv");
  for (i = 0; i <x.length; i++) {
    table += "<tr><td>" +
    x[i].getElementsByTagName("Descripcion")[0].childNodes[0].nodeValue  
  +
    "</td><td>" +

    x[i].getElementsByTagName("precio")[0].childNodes[0].nodeValue +
    "</td></tr>";
  }
  document.getElementById("demo").innerHTML = table;
}
</script>

The actual script only display all the information, but I want to display only the tags contained on "tab_inv" with the tag "code" on value 10 222.

thanks !