RetrieveAllEntities in Javascript

How to get in Javascript all the information regarding entities,attribute and relation:

var xml = "" +
"" +
"" +
GenerateAuthenticationHeader() +
" " +
" " +
" " +
" All" +
" " +
" " +
" " +
"" +
"";
var xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
xmlHttpRequest.Open("POST", "/mscrmservices/2007/MetadataService.asmx",false);
xmlHttpRequest.setRequestHeader("SOAPAction","http://schemas.microsoft.com/crm/2007/WebServices/Execute");
xmlHttpRequest.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
xmlHttpRequest.setRequestHeader("Content-Length", xml.length);
xmlHttpRequest.send(xml);
var resultXml = xmlHttpRequest.responseXML;
alert(resultXml.xml);


Enjoy,
Rami Heleg