CRM 2011 - javascript to retrieve data from lookup entity and map fields

function getcontactdetails() {
    var EntityName, EntityId,LookupFieldObject;
    var Name = "";      
    var resultXml;
    LookupFieldObject = Xrm.Page.data.entity.attributes.get('jmh_customer');
    if (LookupFieldObject.getValue() != null) {
        EntityId = LookupFieldObject.getValue()[0].id;
        EntityName = LookupFieldObject.getValue()[0].entityType;
        resultXml = RetrieveEntityById(EntityName, EntityId, 'jmh_title,fullname,address1_line1');
        if (resultXml != null && resultXml.selectSingleNode('//q1:jmh_title') != null) {
            Name = Name + resultXml.selectSingleNode('//q1:jmh_title').nodeTypedValue;
       }
       if (resultXml != null && resultXml.selectSingleNode('//q1:fullname') != null) {
           Name = Name +" "+ resultXml.selectSingleNode('//q1:fullname').nodeTypedValue;
       }
       if (resultXml != null && resultXml.selectSingleNode('//q1:address1_line1') != null) {
           Xrm.Page.data.entity.attributes.get('jmh_addressline1').setValue(resultXml.selectSingleNode('//q1:address1_line1').nodeTypedValue);
       }

}

//Do not make any changes
function RetrieveEntityById(prmEntityName, prmEntityId, prmEntityColumns) {
    var resultXml, errorCount, msg, xmlHttpRequest, arrayEntityColumns, xmlEntityColumns;
    arrayEntityColumns = prmEntityColumns.split(",");
    for (var i = 0; i < arrayEntityColumns.length; i++) {
        xmlEntityColumns += "<q1:Attribute>" + arrayEntityColumns[i] + "</q1:Attribute>";
    }
    var authenticationHeader = Xrm.Page.context.getAuthenticationHeader();
    //Prepare the SOAP message.
    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'>" +
    authenticationHeader +
    "<soap:Body>" +
    "<Retrieve xmlns='http://schemas.microsoft.com/crm/2007/WebServices'>" +
    "<entityName>" + prmEntityName + "</entityName>" +
    "<id>" + prmEntityId + "</id>" +
    "<columnSet xmlns:q1='http://schemas.microsoft.com/crm/2006/Query' xsi:type='q1:ColumnSet'>" +
    "<q1:Attributes>" +
    xmlEntityColumns +
   "</q1:Attributes>" +
    "</columnSet>" +
    "</Retrieve></soap:Body></soap:Envelope>";
    //call function to create Soap Request to ms crm webservice
    xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
    xmlHttpRequest.Open("POST", "/mscrmservices/2007/CrmService.asmx", false);
    xmlHttpRequest.setRequestHeader("SOAPAction", "http://schemas.microsoft.com/crm/2007/WebServices/Retrieve");
    xmlHttpRequest.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
    xmlHttpRequest.setRequestHeader("Content-Length", xml.length);
    xmlHttpRequest.send(xml);
    resultXml = xmlHttpRequest.responseXML;
    var errorCount = resultXml.selectNodes('//error').length;
    if (errorCount != 0) {
        var msg = resultXml.selectSingleNode('//description').nodeTypedValue;
        alert("Error Message : " + msg);
    }
    else {
        return resultXml;
    }
}
Thanks to
Athul MT

Reference :
http://worldofdynamics.blogspot.in/2011/06/microsoft-dynamics-crm-2011-retrieve.html

Note:
to set lookup field
  if (resultXml != null && resultXml.selectSingleNode('//q1:defaultuomid') != null) {
         var lookupValue = new Array();
            lookupValue[0] = new Object();
            lookupValue[0].id = resultXml.selectSingleNode('//q1:defaultuomid').nodeTypedValue;
            lookupValue[0].name = resultXml.selectSingleNode('//q1:defaultuomid').getAttribute("name");
             lookupValue[0].entityType =  resultXml.selectSingleNode('//q1:defaultuomid').getAttribute("type");

            Xrm.Page.data.entity.attributes.get('uomid').setValue(lookupValue);
        }