/**
 * http get request with success and fail callback
 * handles xml and json data
 */
function httpGet(url, onSuccess, onFail){
  var request = new XMLHttpRequest();
  request.open('GET', url, true);
  //request.setRequestHeader('Accept', 'application/json;odata=nometadata');
  //request.setRequestHeader('Content-Type', 'application/json;odata=nometadata');
  request.onload = function (e) {
      if (request.readyState === 4) {
          // Check if the get call was successful
          if (request.status === 200) {
              // console.log("response", request);

              var data = "";
              if(request.responseXML) {
                  var nodeName = "d:MinorVersion";
                  var tag = request.responseXML.getElementsByTagName(nodeName)[0];
                  var val = "";
                  if(tag) val = tag.childNodes[0].nodeValue;
                  data = val;
              }
              else {
                  var json = JSON.parse(request.response);
                  data = json.value;
              }
              //console.log("data", data);

              if(onSuccess) onSuccess(data);
          } else {
              if(onFail) onFail(request);
          }
      }
  };
  request.onerror = function (e) {
      if(onFail) onFail(e);
  };
  request.send(null);
}