我很确定，如果您为每个调用 实例化一个新对象 ，则可以跟踪每个请求：

var oXhr;

    oXhr = new XMLHttpRequest();
    oXhr.id = (new Date()).getTime(); /* just an example. It might be flawed if you process requests more than once per ms */

    oXhr.onreadystatechange = function() {
        if (oXhr.readyState == 4 && (oXhr.status == 200)) {
            //do your stuff here
            console.log(this.id);
        }
    }