javascript dynamic data loading progress bar

JavaScript dynamic data loading progress bar

i tried some of the codes found here but i am not able to get result

    var req = new XMLHttpRequest();  

    req.addEventListener("progress", onUpdateProgress);  
    req.addEventListener("load", onTransferComplete);  
    req.addEventListener("error", onTransferFailed);  
    req.addEventListener("abort", onTransferFailed);  

    req.open("GET", "http://stackoverflow.com/questions/3790471/xmlhttprequest-js-image-loading");  
    req.send();  

    function onUpdateProgress(e) {  
        var percent_complete = e.loaded/e.total;
        console.log(percent_complete);      
    }  

    function onTransferFailed(e) {  
        alert("Something went wrong. Please try again.");  
    }

    function onTransferComplete(e) {  
        //Problem  
    } 

i should get the percent load in console, but i am not able to get it