updating url parameters

updating url parameters of iFrame

<script>
function ready(fn) {
  if (document.readyState != 'loading'){
    fn();
  } else {
    document.addEventListener('DOMContentLoaded', fn);
  }
}
ready(function () {
  var username = QueryString.Username,
      surveyIFrame = document.querySelector('#zohoSurvey');
  surveyIFrame.src += "?Username=" + username;
  surveyIFrame.style.display = "block";
});
//courtesy of http://stackoverflow.com/a/979995
var QueryString = function () {
  // This function is anonymous, is executed immediately and 
  // the return value is assigned to QueryString!
  var query_string = {};
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
        // If first entry with this name
    if (typeof query_string[pair[0]] === "undefined") {
      query_string[pair[0]] = decodeURIComponent(pair[1]);
        // If second entry with this name
    } else if (typeof query_string[pair[0]] === "string") {
      var arr = [ query_string[pair[0]],decodeURIComponent(pair[1]) ];
      query_string[pair[0]] = arr;
        // If third or later entry with this name
    } else {
      query_string[pair[0]].push(decodeURIComponent(pair[1]));
    }
  } 
    return query_string;
}();
</script>

<iframe id="zohoSurvey" src="https://survey.zohopublic.com/zs/jACNEl" style="display:none; height: 700px; width: 900px;" width="300" height="150" frameborder="0" marginwidth="0" marginheight="0" scrolling="auto"></iframe>