如何用 JavaScript 中的 XMLHttpRequest 替换所有请求中的标头令牌？

var open = XMLHttpRequest.prototype.open;
var send = XMLHttpRequest.prototype.send;
var method = "";
var url ="";
XMLHttpRequest.prototype.open = function (_method,_url) {

method = _method;
url = _url;
open.apply(this, [].slice.call(arguments)); 
};

XMLHttpRequest.prototype.send = function (data) {
var xml2 = new XMLHttpRequest();
xml2.open(method, url,true); 
xml2.setRequestHeader('Authorization', "aaa");
send.call(xml2, data);
};