$.ajax({
    url: url,
    data: para,
    dataType:'json',
    xhr: function () {
    var xhr = new window.XMLHttpRequest();
    xhr.addEventListener("progress", function (evt) {
        console.log(evt)
    }, false);
    return xhr;
    },
    success: function(d) {
        ///////
        console.log(d)
    }
})

xhr.upload.addEventListener 上传！！

lengthComputable 总是 false。如果能计算，用 loaded/total 就是百分比

Network 右键 Copy Response Headers

稍微的不严格（json 必须双引号！都会导致 lengthComputable: false）！！！！！！

Content-Encoding:gzip 也不行！！！

header(“Content-Encoding: compress”); //可以！！！

HTTP/1.1 200 OK
Date: Mon, 15 Sep 2014 04:37:56 GMT
Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch
X-Powered-By: PHP/5.3.15
Content-Length: 9703
Keep-Alive: timeout=15, max=100
Connection: Keep-Alive
Content-Type: text/html

HTTP/1.1 200 OK
Date: Mon, 15 Sep 2014 07:09:02 GMT
Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch
Last-Modified: Mon, 15 Sep 2014 03:10:07 GMT
ETag: “59aa3f7-414-50311f8cc01c0”
Accept-Ranges: bytes
Content-Length: 1044
Keep-Alive: timeout=15, max=99
Connection: Keep-Alive
Content-Type: application/json

<? ob_start(); ?>
{
“name”: “guoshuang test”
}

<?
$length = ob_get_length();
header(“Content-Length: “.$length);
//header(“X-Content-Length: “.$length);
ob_end_flush();
?>

http://www.jnecw.com/p/1340