CRM 4.0 : Check current user's security role using JavaScript

It's a common question about how to show/hide fields based on user's security roles.
Ronald Lemmen had a very popular post on his blog about how to use 'RemoteCommand' to achieve that in CRM 3.0. Because 'RemoteCommand' is for internal use and unsupported, it doesn't work in CRM 4.0.
Michael H?hne also had a great post about how to access web service using client-side JavaScript. Since CRM 4.0 web service EndPoint changed, some people get 401 authorization error.

Here's code which works great in CRM 4.0, the function UserHasRole("ROLE_NAME") returns true if the current has the role, returns false if it doesn't. GetCurrentUserRoles() function generated by Michael H?hne's tool with some changes. Thanks for Regan who point out that using GenerateAuthenticationHeader() instead of hard-coding the Organization's Name.

//check if the current user has the 'System Administrator' role
alert(UserHasRole("System Administrator"));

function UserHasRole(roleName)
{
 //get Current User Roles, oXml is an object
 var oXml = GetCurrentUserRoles();
 if(oXml != null)
 {
  //select the node text
  var roles = oXml.selectNodes("//BusinessEntity/q1:name");
  if(roles != null)
  {
   for( i = 0; i < roles.length; i++)
   {
    if(roles[i].text == roleName)
    {
     //return true if user has this role
     return true;
    }
   }
  }
 }
 //otherwise return false
 return false;
}

function GetCurrentUserRoles()
{
 var xml = "" +
 "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
 "<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">" +
 GenerateAuthenticationHeader() +
 " <soap:Body>" +
 " <RetrieveMultiple xmlns=\"http://schemas.microsoft.com/crm/2007/WebServices\">" +
 " <query xmlns:q1=\"http://schemas.microsoft.com/crm/2006/Query\" xsi:type=\"q1:QueryExpression\">" +
 " <q1:EntityName>role</q1:EntityName>" +
 " <q1:ColumnSet xsi:type=\"q1:ColumnSet\">" +
 " <q1:Attributes>" +
 " <q1:Attribute>name</q1:Attribute>" +
 " </q1:Attributes>" +
 " </q1:ColumnSet>" +
 " <q1:Distinct>false</q1:Distinct>" +
 " <q1:LinkEntities>" +
 " <q1:LinkEntity>" +
 " <q1:LinkFromAttributeName>roleid</q1:LinkFromAttributeName>" +
 " <q1:LinkFromEntityName>role</q1:LinkFromEntityName>" +
 " <q1:LinkToEntityName>systemuserroles</q1:LinkToEntityName>" +
 " <q1:LinkToAttributeName>roleid</q1:LinkToAttributeName>" +
 " <q1:JoinOperator>Inner</q1:JoinOperator>" +
 " <q1:LinkEntities>" +
 " <q1:LinkEntity>" +
 " <q1:LinkFromAttributeName>systemuserid</q1:LinkFromAttributeName>" +
 " <q1:LinkFromEntityName>systemuserroles</q1:LinkFromEntityName>" +
 " <q1:LinkToEntityName>systemuser</q1:LinkToEntityName>" +
 " <q1:LinkToAttributeName>systemuserid</q1:LinkToAttributeName>" +
 " <q1:JoinOperator>Inner</q1:JoinOperator>" +
 " <q1:LinkCriteria>" +
 " <q1:FilterOperator>And</q1:FilterOperator>" +
 " <q1:Conditions>" +
 " <q1:Condition>" +
 " <q1:AttributeName>systemuserid</q1:AttributeName>" +
 " <q1:Operator>EqualUserId</q1:Operator>" +
 " </q1:Condition>" +
 " </q1:Conditions>" +
 " </q1:LinkCriteria>" +
 " </q1:LinkEntity>" +
 " </q1:LinkEntities>" +
 " </q1:LinkEntity>" +
 " </q1:LinkEntities>" +
 " </query>" +
 " </RetrieveMultiple>" +
 " </soap:Body>" +
 "</soap:Envelope>" +
 "";

 var xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");

 xmlHttpRequest.Open("POST", "/mscrmservices/2007/CrmService.asmx", false);
 xmlHttpRequest.setRequestHeader("SOAPAction"," http://schemas.microsoft.com/crm/2007/WebServices/RetrieveMultiple");
 xmlHttpRequest.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
 xmlHttpRequest.setRequestHeader("Content-Length", xml.length);
 xmlHttpRequest.send(xml);

 var resultXml = xmlHttpRequest.responseXML;
 return(resultXml);
}

Due to Bloger's format issue, I have rewrite the code, it should work for everyone now.:)