Conditionally load jQuery via loadScript

gistfile1.js

/* Sample JavaScript file added with ScriptTag resource. 
This sample file is meant to teach best practices.
Your app will load jQuery if it's not defined. 
Your app will load jQuery if jQuery is defined but is too old, e.g. < 1.7. 
Your app does not change the definition of $ or jQuery outside the app. 
*/

(function(){
  
/* Load Script function we may need to load jQuery from the Google's CDN */
/* One source: http://snipplr.com/view/18756/loadscript/ */

var loadScript = function(url, callback){
 
  var script = document.createElement("script");
  script.type = "text/javascript";

  // If the browser is Internet Explorer.
  if (script.readyState){ 
    script.onreadystatechange = function(){
      if (script.readyState == "loaded" || script.readyState == "complete"){
        script.onreadystatechange = null;
        callback();
      }
    };
  // For any other browser.
  } else {
    script.onload = function(){
      callback();
    };
  }

  script.src = url;
  document.getElementsByTagName("head")[0].appendChild(script);
    
};

/* This is my app's JavaScript */
var myAppJavaScript = function($){
  // Do this and do that, using $.
  $('body').append('<p>Your app is using jQuery version '+$.fn.jquery+'</p>');
};

/* If jQuery has not yet been loaded or if it has but it's too old for our needs,
we will load jQuery from the Google CDN, and when it's fully loaded, we will run
our app's JavaScript. Set your own limits here, the sample's code below uses 1.7
as the minimum version we are ready to use, and if the jQuery is older, we load 1.9. */
if ((typeof jQuery === 'undefined') || (parseInt($.fn.jquery.split('.')[1]) < 7)) {
  loadScript('//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js', function(){
    var jQuery191 = jQuery.noConflict(true);
    myAppJavaScript(jQuery191);
  });
} else {
  myAppJavaScript(jQuery);
}

})();