How to get a SharePoint-UserField with JavaScript?

// Get values
var ctx='ctl00_m_g_e5a1501a_..._ctl04_ctl00_ctl00_UserField';
var values=getUplevel(ctx);
alert(values);

// Set values
var xml='<Entities Append="False" Error="" Separator=";" MaxHeight="3">'+
    '<Entity Key="DOMAIN\loginname" DisplayText="Display Name" IsResolved="True" Description="DOMAIN\loginname">'+
    	'<ExtraData>'+
    		'<ArrayOfDictionaryEntry xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">'+
    			'<DictionaryEntry><Key xsi:type="xsd:string">DisplayName</Key><Value xsi:type="xsd:string">Display Name</Value></DictionaryEntry>'+
    			'<DictionaryEntry><Key xsi:type="xsd:string">Email</Key><Value xsi:type="xsd:string">[email protected]</Value></DictionaryEntry>'+
    			'<DictionaryEntry><Key xsi:type="xsd:string">SPUserID</Key><Value xsi:type="xsd:string">1</Value></DictionaryEntry>'+
    			'<DictionaryEntry><Key xsi:type="xsd:string">PrincipalType</Key><Value xsi:type="xsd:string">User</Value></DictionaryEntry>'+
    		'</ArrayOfDictionaryEntry>'+
    	'</ExtraData>'+
    	'<MultipleMatches />'+
    '</Entity>'+
'</Entities>';
EntityEditorCallback(xml,ctx);

function getParentElementByTagName(baseNode, tagName)
{
  var currNode;

  if(baseNode !== null)
  {
    currNode = baseNode.parentNode;

    while((currNode !== null) && (currNode.nodeName != tagName))
    {
      currNode = currNode.parentNode;
    }

    return currNode;
  }
  else
  {
    return null;
  }
}

function getPeoplePickerCell(columnName)
{
  var search = 'FieldName="' + columnName + '"';

  var nodes = document.getElementsByTagName("TEXTAREA");

  for(var i=0; i < nodes.length; i++)
  {
    if(nodes[i].title == "People Picker")
    {
      var outerCell = getParentElementByTagName(nodes[i], "SPAN").parentNode.parentNode;

      if(outerCell.innerHTML.indexOf(search) > 0)
      {
        return nodes[i].parentNode;
      }
    }
  }

  return null;
}

function getSPPeoplePicker(columnName, value)
{
  var cell = getPeoplePickerCell(columnName);

  if(cell !== null)
  {
    return cell.childNodes[0].innerHTML;
  }
  else
  {
    return null;
  }
}

function setSPPeoplePicker(columnName, value)
{
  var cell = getPeoplePickerCell(columnName);

  if(cell !== null)
  {
    cell.childNodes[0].innerHTML = value;
    cell.childNodes[1].value = value;
  }
}

function disableSPPeoplePicker(columnName)
{
  var cell = getPeoplePickerCell(columnName);

  if(cell !== null)
  {
    disableElement(cell.childNodes[0]);
    disableElement(cell.childNodes[1]);
  }
}

function enableSPPeoplePicker(columnName)
{
  var cell = getPeoplePickerCell(columnName);

  if(cell !== null)
  {
    enableElement(cell.childNodes[0]);
    enableElement(cell.childNodes[1]);
  }
}