关闭`@grant none`会破坏我的Greasemonkey脚本？

Question

我在Facebook主页上运行此脚本.它在底部的底座中获得所有对话并得到它们的__FB_TOKENs.

// ==UserScript==
// @name MyScript
// @namespace MyNameSpance
// @include /https?://(www.)?facebook.com(/.*)?/
// @require http://code.jquery.com/jquery-2.1.0.min.js
// @version 0.0.0
// @grant none
// ==/UserScript==
(function () {
  // Don't run on frames or iframes
  if (window.top != window.self) {
    return ;
  }

  window.addEventListener('load', function () {

    var element = $('.fbNubGroup.clearfix.videoCallEnabled');
    console.log('SCRIPT ELEMENT: ', element); // is displayed on the console

    var children = element.children();
    console.log('SCRIPT CHILDREN: ', children); // is displayed on the console

    for (var i = 0; i < children.length; i++) {
      var child = $(children[i]);
      console.log('SCRIPT CHILD: ', child); // is displayed on the console

      /*
      child :
        Object [div.someClasses]
          + 0: div.someClasses
            + __FB_TOKEN: [ 267 ]
      */

      console.log('SCRIPT CHILD[0]: ', child[0]); // is displayed on the console
      console.log('SCRIPT CHILD[0].__FB_TOKEN:', child[0].__FB_TOKEN); // UNDEFINED

      var key = child[0].__FB_TOKEN[0];
      console.log('SCRIPT KEY: ', key); // not displayed
    }
  }, false);
}) ();

随着@grant none,它按预期工作,我得到:

但是,如果我@grant none改为@grant GM_xmlhttpRequest,脚本将不再起作用.它给:

并在该child[0].__FB_TOKEN行上抛出异常.

我不明白为什么,因为CHILD[0]没有改变:

为什么要更改@grant none破坏脚本？

Answer 1

当您切换@grant none到时@grant GM_xmlhttpRequest,Greasemonkey会重新打开沙盒,作为副作用.
_{(坦率地说,所有GM开发人员和脚本都应该始终使用沙箱运行 - 极少数例外.这避免了"定时炸弹"编码问题以及像这个问题一样的头脑风暴.)}

JavaScript对象,数组,变量和函数无法跨越沙箱.但unsafeWindow作为有限的解决方法提供给Greasemonkey范围.

这个问题也很重要:

1. Greasemonkey(和Firefox)刚刚关闭了一些以前可能使用的解决方案unsafeWindow.
2. jQuery是一个特殊情况,并且非常难以将非DOM对象用于沙箱.

解:

1. 由于__FB_TOKEN是一个数组,您必须使用unsafeWindow它来跨越沙箱.
2. 在这种情况下尝试使用jQuery会产生令人无法接受的高头痛与结果比率; 所以使用普通的DOM方法.

将所有内容放在一起脚本变为:

// ==UserScript==
// @name        _MyScript
// @namespace   MyNameSpace
// @include     /https?://(www.)?facebook.com(/.*)?/
// @require     http://code.jquery.com/jquery-2.1.0.min.js
// @version     0.0.0
// @grant       GM_xmlhttpRequest
// ==/UserScript==
(function () {
    // Don't run on frames or iframes
    if (window.top != window.self) {
        return;
    }
    window.addEventListener ('load', function () {
        /*--- This unsafeWindow is key. After that, don't use any jQuery
            while trying to get at javascript objects like __FB_TOKEN.
        */
        var element = unsafeWindow.document.querySelector (
            '.fbNubGroup.clearfix.videoCallEnabled'
        );
        /*-- Used console.info to make it easier to spot messages buried
            in all the Facebook console crud.
        */
        console.info ('SCRIPT ELEMENT: ', element);

        var children = element.children;
        console.info ('SCRIPT CHILDREN: ', children);

        for (var i = 0; i < children.length; i++) {
            var child = children[i];
            console.info ('SCRIPT CHILD: ', child);

            /*
            child :
              Object [div.someClasses]
                + 0: div.someClasses
                  + __FB_TOKEN: [ 267 ]
            */
            console.info ('SCRIPT CHILD: ', child);
            console.info ('SCRIPT CHILD.__FB_TOKEN:', child.__FB_TOKEN);

            var key = child.__FB_TOKEN[0];
            console.info ('SCRIPT KEY: ', key);
        }
    }, false);
} ) ();