How to get progress when uploading file VIA XMLHttpRequest

I am wondering how to get the progress of a file upload using XMLHTTPRequest. In Firefox the onprogress method does not fire at all, and in chrome it only fires after the file has finished uploading.

function fileUpload(file)
{
    var formData = new FormData();
    formData.append('file', file);

    var xhr = new XMLHttpRequest();
    xhr.onprogress = function(e)
    {
        alert('progress');
    };

    xhr.open('POST', 'post.php', true);

    xhr.send(form开发者_如何转开发Data);  // multipart/form-data
}

Try xhr.upload.onprogress. In the XMLHttpRequest2 spec XMLHttpRequest have upload attribute.

The ability to register for progress events. Both for downloads (put listeners on the XMLHttpRequest object itself) and uploads (put listeners on the XMLHttpRequestUpload object, returned by the upload attribute). http://dev.w3.org/2006/webapi/XMLHttpRequest-2/#differences