function getDemographicData() {
  var url = "/data";

  var dataRequest = new XMLHttpRequest();
  dataRequest.onreadystatechange = function() {
    console.log(dataRequest.readyState);
    if (dataRequest.readyState == 4 && dataRequest.status == 200) {
      var data = JSON.parse(dataRequest.responseText);
      console.log(data);
      // do stuff
      dataRequest = null;
    }
  };
  dataRequest.open("GET", url, true);
  dataRequest.send(null);
}