欺骗xmlhttprequest (greasemonkey)

Question

我正在阻止一个XMLHttpRequest从greasemonkey，但页面错误时，它没有得到响应。所以我试着欺骗，好像收到了回应一样。无意中，似乎XMLHttpRequest的字段是只读的。所以我创建了一个假对象：

fakeresponse = "for (;;);"+JSON.stringify(fakeresponse);


var xhr2 = {};
xhr2.readyState = 0;
if(xhr.onreadystatechange!==undefined) xhr.onreadystatechange.call(xhr2);
xhr2.readyState = 1;
if(xhr.onreadystatechange!==undefined) xhr.onreadystatechange.call(xhr2);
xhr2.readyState = 2;
if(xhr.onreadystatechange!==undefined) xhr.onreadystatechange.call(xhr2);
xhr2.readyState = 3;
if(xhr.onreadystatechange!==undefined) xhr.onreadystatechange.call(xhr2);
xhr2.response = fakeresponse;
xhr2.responseText = fakeresponse;
xhr2.responseXML = fakeresponse;
xhr2.status = 200;
xhr2.readyState = 4;

if(xhr.onreadystatechange!==undefined) xhr.onreadystatechange.call(xhr2);

目标是：

Object {response: "for (;;);{"__ar":1,"payload":{"actions":[{"..."},"bootloadable":{},"ixData":{},"lid":"0"}", responseText: "for (;;);...", responseXML: "for (;;);....", status: 200, readyState: 4}

但什么都没发生..。还有其他方法可以模拟这个吗，或者我必须深入到调试器中去？另外，页面使用的是库而不是纯的xhr对象，这会是一个问题吗？

Answer 1

(function(xhr, value){
Object.defineProperty(xhr, "response", {
  get: function() {
    return value;
  }
});

Object.defineProperty(xhr, "responseText", {
  get: function() {
    return value;
  }
});

Object.defineProperty(xhr, "responseXML", {
  get: function() {
    return value;
  }
});
Object.defineProperty(xhr, "status", {
  get: function() {
    return 200;
  }
});
})(xhr, fakeresponse);

Object.defineProperty(xhr, "readyState", {
  get: function() {
    return 4;
  }
});

if(xhr.onreadystatechange!==undefined) xhr.onreadystatechange();