Non blocking script not working with jQuery

问题

I'm working on a non-blocking script and it's works fine but when i try to load jQuery, its loads but i cant execute jQuery functions like this simple alert:

    $(document).ready(function(){
        alert('jQuery loaded !');
    });

Here is what im trying:

    var xhrObj = XMLHttpRequest();
    xhrObj.onreadystatechange = 
        function(){
            if(xhrObj.readyState == 4){
                var element = document.createElement("script");             
                document.getElementsByTagName('head')[0].appendChild(element);
                element.text = xhrObj.responseText;
            }
        };
    xhrObj.open('GET', 'js/jquery.js', true);
    xhrObj.send('');

and tried it too:

var js = document.createElement('script');
js.src = 'js/jquery.js';
var head = document.getElementsByTagName('head')[0];
head.appendChild(js);

Here is the result of Firebug error:

ReferenceError: $ is not defined    

$(document).ready(function(){

but when i check Firebug network, jQuery is loaded....

Need some help.. Thanks !

来源：https://stackoverflow.com/questions/15855149/non-blocking-script-not-working-with-jquery