how to read xml file with many nodes with javascript -

i have registrationresponsemessages.xml:

<messages>   <error>     <code id="501">couldn't retrieve html document because of server-configuration problems.</code>     <code id="502">server busy, site may have moved ,or lost dial-up internet connection.</code>   </error>   <success></success> </messages> 

trying read contents of code id 501 , 502 javascript, not works.

if (window.xmlhttprequest) {// code ie7+, firefox, chrome, opera, safari             xmlhttp = new xmlhttprequest();         }         else {// code ie6, ie5             xmlhttp = new activexobject("microsoft.xmlhttp");         }         xmlhttp.open("get", "registrationresponsemessages.xml", false);         xmlhttp.send();         xmldoc = xmlhttp.responsexml;          document.getelementbyid("errorcode403").innerhtml = getelementsbytagname(501)[0].childnodes[0].nodevalue); 

displaying here:

<label id="errorcode403" style="font-weight: 600; color: red;">give error</label> 

what problem?

it's ajax, have wait data returned, have access right way:

var xmlhttp;  if (window.xmlhttprequest) {     xmlhttp = new xmlhttprequest(); } else {     xmlhttp = new activexobject("microsoft.xmlhttp"); }  xmlhttp.onload = function() {     var xmldoc = this.responsexml,         value  = xmldoc.getelementsbytagname('501')[0].childnodes[0].nodevalue;     document.getelementbyid("errorcode403").innerhtml = value; }  xmlhttp.open("get", "registrationresponsemessages.xml", false); xmlhttp.send(); 

not sure traversal in xml, 501 sounds strange tagname ?

edit:

to list of id's inside onload handler:

xmlhttp.onload = function() {     var xmldoc = this.responsexml,      var codes = xmldoc.getelementsbytagname('code');     var array = [];      (var i=0; i<codes.length; i++) {           array.push( codes[i].id );     }      console.log(array); }