//  getUrl
//  Will initate the http request for data.
function getUrl(url,fn) {
  if (url && fn) {
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.open("GET", url, true);
    xmlhttp.onreadystatechange = function() {
      if (xmlhttp.readyState == 4) {
        fn(xmlhttp.responseXML);
      }
    };
    xmlhttp.send('');
  } else {
    alert('url or function not specified!');
  }
}

//  trim functions
//  will trim whitespace from strings
String.prototype.trim=function(){ 
  return this.replace(/^\s*|\s*$/g,'');
}
String.prototype.ltrim=function(){
  return this.replace(/^\s*/g,'');
}
String.prototype.rtrim=function(){
  return this.replace(/\s*$/g,'');
}

//  CheckResultIsOk
//  Will check the XML data you've return for <error_code>x</error_code>
//  and returns the error to the user if found.
function checkResultIsOk(xml) {
  if (!xml) {
    //xml data was empty. Result was not ok.
    return false;
  }
  if (xml.getElementsByTagName('error_code')[0].firstChild.data && 
    Math.abs(xml.getElementsByTagName('error_code')[0].firstChild.data.trim()) > 0) {
    //error has been supplied
    alert('Error ' + xml.getElementsByTagName('error_code')[0].firstChild.data + ': ' +
      xml.getElementsByTagName('error')[0].firstChild.data.trim());
    return false;
  } else {
    //no errors!
    return true;
  }
}