如何在Firefox的WebExtension中覆盖XMLHttpRequest

我正在尝试覆盖Firefox的WebExtension中的 XMLHttpRequest.protype.open 方法.我已经在内容脚本中编写了以下代码

I am trying to override the XMLHttpRequest.protype.open method in Firefox's WebExtension. I have written a following code in content script

var oldOpen = XMLHttpRequest.prototype.open;
XMLHttpRequest.prototype.open = function (method, url, async, user, pass) {
    console.log("url :"+url+"\n method: "+method);
    oldOpen.apply(this,arguments);
};

但是此代码不起作用.如果有人知道如何重写XMLHttpRequest.prototype.open方法，请告诉我.

But this code is not working. If anyone know that how to override the XMLHttpRequest.prototype.open method then please let me know.