Firefox 附加组件 window.navigator.userAgent 错误：窗口未定义

我想得到userAgent https://developer.mozilla.org/en-US/docs/Web/API/NavigatorID/userAgent并想对其进行一些解析：

我的代码是：

var userAgentInfo = {
    userAgent: null,

    init: function() {
        this.userAgent = window.navigator.userAgent;//ERROR
    },

    getOS: function(UA) {
        //Some logic
    },

    getDevice: function(UA) {
        //Some logic
    },
    getBrowser: function(UA) {
        //Some logic
    },
};

每当我尝试启动/测试此扩展时，我都会收到以下错误：

Running tests on Firefox 24.3.0/Gecko 24.3.0 ({ec8030f7-c20a-464f-9b0e-13a3a9e97384}) under linux/x86-gcc3.
Error: ReferenceError: window is not defined 
 Traceback (most recent call last):
  File "resource://jid1-u33krawc1uacsa-at-jetpack/amazon_rewriter/tests/test-main.js", line 1, in 

我怎样才能得到userAgent这里没有获取窗口和导航器对象？

Firefox 附加组件通常运行在全局范围内window对象未定义（是否定义取决于当前运行的代码部分的输入方式）。如果要使用与窗口对象关联的方法/对象，最简单的方法是获取对适当窗口对象的引用window目的。对于某些/许多事情，可以在不获取此类引用的情况下执行此操作，但通常更容易获取对最新浏览器窗口的引用。

如果存在浏览器窗口（在某些情况下，您可能在不存在浏览器窗口的情况下运行，例如在启动时），您可以获得对最新浏览器的引用window, document, and gBrowser with:

if (window === null || typeof window !== "object") {
    //If you do not already have a window reference, you need to obtain one:
    //  Add/remove a "/" to comment/un-comment the code appropriate for your add-on type.
    //* Add-on SDK:
    var window = require('sdk/window/utils').getMostRecentBrowserWindow();
    //*/
    /* Overlay and bootstrap (from almost any context/scope):
    var window=Components.classes["@mozilla.org/appshell/window-mediator;1"]
                         .getService(Components.interfaces.nsIWindowMediator)
                         .getMostRecentWindow("navigator:browser");        
    //*/
}
if (typeof document === "undefined") {
    //If there is no document defined, get it
    var document = window.content.document;
}
if (typeof gBrowser === "undefined") {
    //If there is no gBrowser defined, get it
    var gBrowser = window.gBrowser;
}

缺乏全球性window对象可用是许多人遇到的问题。

参考：

1. SDK: 窗口/实用程序 https://developer.mozilla.org/en-US/Add-ons/SDK/Low-Level_APIs/window_utils
2. SDK: windows https://developer.mozilla.org/en-US/Add-ons/SDK/High-Level_APIs/windows
3. nsIWindowMediator https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/Reference/Interface/nsIWindowMediator
4. 在 chrome 代码中使用 Windows https://developer.mozilla.org/en-US/docs/Working_with_windows_in_chrome_code