Jquery get current url and add/push parameter

function.js

function dropdownChange(){
  var byDate = document.getElementById('filter-by-date').value;
  var myUrl = addQSParm('cat_type',cat_type);
  var myUrl = addQSParm('keyword',sKeyword, myUrl);
  window.location.href = myUrl;
}


/**************************************************
@ Constructing a URL with parameters using jQuery 
***************************************************/
function addQSParm(name, value, myUrl = '') {
  if(myUrl == ''){
    var myUrl = window.location.origin+''+window.location.pathname;
  }

  var re = new RegExp("([?&]" + name + "=)[^&]+", "");

  function add(sep) {
      myUrl += sep + name + "=" + encodeURIComponent(value);
  }

  function change() {
      myUrl = myUrl.replace(re, "$1" + encodeURIComponent(value));
  }
  if (myUrl.indexOf("?") === -1) {
      add("?");
  } else {
      if (re.test(myUrl)) {
          change();
      } else {
          add("&");
      }
  }
  return myUrl;
}