javascript - 将 Firefox 30 之前的 Greasemonkey 脚本迁移到 GM4+ 时，如何替换 unsafeWindow？

Question

我试图在一个 Greasemonkey 脚本中获取对我网页上存在的 jQuery 版本的引用，该脚本在 Firefox 30 之前一直有效。在我的定义下方的评论中，我可以找到另外两个引用，但我只是得到 ReferenceError: $ is not defined 或 ReferenceError: jQuery is not defined 当我尝试访问窗口对象上的 jQuery 时。

var $ = unsafeWindow.jQuery;
//var jQuery = window.jQuery; // From https://stackoverflow.com/questions/24802606/binding-to-an-event-of-the-unsafewindow-in-firefox-30-with-greasemonkey-2-0
//var jQuery = $ || window.wrappedJSObject.$; // https://github.com/greasemonkey/greasemonkey/issues/2700#issuecomment-345538182
function addAccountNameToTitle(jNode) {
  $('title').text(session.name + " | " + $('title').text());
}

waitForKeyElements (".page-breadcrumb", addAccountNameToTitle, false);

/*--- waitForKeyElements():  A handy, utility function that
    does what it says.
*/
function waitForKeyElements (
    selectorTxt,    /* Required: The jQuery selector string that
                        specifies the desired element(s).
                    */
    actionFunction, /* Required: The code to run when elements are
                        found. It is passed a jNode to the matched
                        element.
                    */
    bWaitOnce,      /* Optional: If false, will continue to scan for
                        new elements even after the first match is
                        found.
                    */
    iframeSelector  /* Optional: If set, identifies the iframe to
                        search.
                    */
)
{
    var targetNodes, btargetsFound;

    if (typeof iframeSelector == "undefined")
        targetNodes     = $(selectorTxt);
    else
        targetNodes     = $(iframeSelector).contents ()
                                           .find (selectorTxt);

    if (targetNodes  &&  targetNodes.length > 0) {
        /*--- Found target node(s).  Go through each and act if they
            are new.
        */
        targetNodes.each ( function () {
            var jThis        = $(this);
            var alreadyFound = jThis.data ('alreadyFound')  ||  false;

            if (!alreadyFound) {
                //--- Call the payload function.
                actionFunction (jThis);
                jThis.data ('alreadyFound', true);
            }
        } );
        btargetsFound   = true;
    }
    else {
        btargetsFound   = false;
    }

    //--- Get the timer-control variable for this selector.
    var controlObj      = waitForKeyElements.controlObj  ||  {};
    var controlKey      = selectorTxt.replace (/[^\w]/g, "_");
    var timeControl     = controlObj [controlKey];

    //--- Now set or clear the timer as appropriate.
    if (btargetsFound  &&  bWaitOnce  &&  timeControl) {
        //--- The only condition where we need to clear the timer.
        clearInterval (timeControl);
        delete controlObj [controlKey]
    }
    else {
        //--- Set a timer, if needed.
        if ( ! timeControl) {
            timeControl = setInterval ( function () {
                    waitForKeyElements (    selectorTxt,
                                            actionFunction,
                                            bWaitOnce,
                                            iframeSelector
                                        );
                },
                500
            );
            controlObj [controlKey] = timeControl;
        }
    }
    waitForKeyElements.controlObj   = controlObj;
}

我正在使用 FF 59.0.2 和 Greasemonkey 4.3

Answer 1

unsafeWindow.jQuery 从来都不是一个好主意，而且很少奏效。另请参阅 Error: Permission denied to access property 'handler' .

处理问题代码的聪明做法是使用@require，如下所示:

// ==UserScript==
// @name     _Changing the title text on some page.
// @match    *://YOUR_SERVER.COM/YOUR_PATH/*
// @require  https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js
// @require  https://gist.github.com/raw/2625891/waitForKeyElements.js
// @grant    GM_addStyle
// @grant    GM.getValue
// ==/UserScript==
//- The @grant directives are needed to restore the proper sandbox.

waitForKeyElements (".page-breadcrumb", addAccountNameToTitle);

function addAccountNameToTitle (jNode) {
    $('title').text (session.name + " | " + $('title').text() );
}

优点:

• 简短、明了。
• 不容易受到更改目标页面上的 javascript 的副作用的影响。特别是，如果目标页面更改了 jQuery 版本。
• 使用快速的本地版本的 jQuery 和 waitForKeyElements。它们存储在本地磁盘上，通常缓存在内存中。没有服务器获取也没有延迟。

注意:如果session是目标页面的全局变量，您可能需要像unsafeWindow.session.name一样访问它。请参阅:How to access `window` (Target page) objects when @grant values are set? .

---

---

---

您声明要使用页面的 jQuery 实例或版本。很少有充分的理由这样做。而这个问题中显示的代码肯定不会从中受益。

但是，如果您的用户脚本不使用任何 GM 函数，您可以通过 @grant none 模式来做到这一点，例如:

// ==UserScript==
// @name     _Changing the title text on some page.
// @match    *://YOUR_SERVER.COM/YOUR_PATH/*
// @require  https://gist.github.com/raw/2625891/waitForKeyElements.js
// @grant    none
// ==/UserScript==

waitForKeyElements (".page-breadcrumb", addAccountNameToTitle);

function addAccountNameToTitle (jNode) {
    $('title').text (session.name + " | " + $('title').text() );
}