Lea Verou's proposal regarding URL class in https://leaverou.github.io/jsux/

myURL.js

!function() {
  var myURL = function(str) {
    this.str      = str;
    this.toString = function() { return str; };
  }

  function createFromString(urlString) {
    return new myURL(urlString);
  }

  function createFromURL(url) {
    return new myURL(url.str);
  }

  function createFromLocation(extraURI) {
    var urlString = window.location.href + (extraURI || "");
    return new myURL(urlString);
  }

  var myURLFactory = {
    createFromString:   createFromString,
    createFromURL:      createFromURL,
    createFromLocation: createFromLocation
  };

  window.myURL        = myURL;
  window.myURLFactory = myURLFactory;
}();

// > myURLFactory.createFromURL(new myURL("http://abre.ai/")) + "ae"
// < "http://abre.ai/ae"
// > myURLFactory.createFromString("http://abre.ai/") + "ae"
// < "http://abre.ai/ae"
// > myURLFactory.createFromLocation("ae") + "opa"
// < "http://www.phpied.com/3-ways-to-define-a-javascript-class/aeopa"