使用 Greasemonkey 删除特定的 javascript 函数答案

【问题标题】：Remove specific javascript function with Greasemonkey使用 Greasemonkey 删除特定的 javascript 函数
【发布时间】：2020-03-06 12:43:54
【问题描述】：

我访问的网站在 HTML 的头部有一个 javascript 文件

<script>(function(d){var config={kitId:'gpn1wjb',scriptTimeout:3000,async:true},h=d.documentElement,t=setTimeout(function(){h.className=h.className.replace(/\bwf-loading\b/g,"")+" wf-inactive";},config.scriptTimeout),tk=d.createElement("script"),f=false,s=d.getElementsByTagName("script")[0],a;h.className+=" wf-loading";tk.src='//use.typekit.net/'+config.kitId+'.js';tk.async=true;tk.onload=tk.onreadystatechange=function(){a=this.readyState;if(f||a&&a!="complete"&&a!="loaded")return;f=true;clearTimeout(t);try{Typekit.load(config)}catch(e){}};s.parentNode.insertBefore(tk,s)})(document);</script>

如何使用 Greasemonkey 禁用/删除/替换此功能？

【问题讨论】：

标签： javascript greasemonkey

【解决方案1】：

没有标准的方法来处理这个问题。您要禁用的功能会在浏览器读取 HTML 的那部分后立即执行，这意味着即使您在文档加载开始时运行用户脚本（使用 @run-at document-start），也无法从 tampermonkey 中删除脚本节点。

您可以尝试利用他们调用setTimeout 的事实。这个想法是在他们调用它的那一刻抛出一个错误，这样他们的代码 sn-p 就不能正常运行。

代码应如下所示。确保您访问的是未沙箱化的 window 对象。

const oldSetTimeout = window.setTimeout;
// replace setTimeout with our hacked version
window.setTimeout = newSetTimeout;
/**
 *
 * @param {function} cb
 * @param {number} delay
 */
function newSetTimeout(cb, delay) {
    // Check if callback contains string we know from the sourcecode
    if (cb && cb.toString().indexOf("bwf-loading")!=-1) {
        // misdeed done, restore normal setTimeout
        window.setTimeout = oldSetTimeout;
        throw new Error("Failing set timeout to kill unwanted script.");
    }
    // otherwise act as normal setTimeout
    else {
        return oldSetTimeout.call(window, arguments);
    }
}

【讨论】：

您是否确保代码在文档开始时正确执行？有一个greasemonkey设置。

【解决方案2】：

采用example from Tomas 并将其更新为与 Greasemonkey v4 一起使用，主要变化是您需要跨上下文导出函数。此示例更改了适合我的用例的 document.body.appendChild 函数，但我还有一些其他函数也使用类似的模式。

const overwriteAC = function(){
  // despite comments in https://stackoverflow.com/questions/48122766/function-not-defined-or-permission-denied-to-access-object-in-greasemonkey/48194770
  // `unsafeWindow.[...]` does not seem to be necessary here
  // however, on other (?) functions e.g. `document.createElement` you will need to
  // use `.bind()` as per comments here
  // https://stackoverflow.com/a/24339478/2640621
  // e.g. `const oldCreateElement = document.createElement.bind(document);`
  const oldAC = document.body.appendChild;
  const newAC = function(node) {
    if (node && "src" in node && node.src.includes("recaptcha")) {
      console.log(`Blocking ${node.src}.`);
      node.src = "";
      node.text = "";
      // `functions` returns a list, `appendChild` only takes one argument so we just pass `node` here instead
      // the first argument to `.call()` changes depending on which function you're modifying
      // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call#parameters
      oldAC.call(document.body, node);
    } else {
      oldAC.call(document.body, node);
    };
  };
  // as per https://www.greasespot.net/2017/09/greasemonkey-4-for-script-authors.html
  // and https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Sharing_objects_with_page_scripts#exportfunction
  // this is required for the page script's scope to access the `newAC()` function
  exportFunction(newAC, document.body, {defineAs:'appendChild'});
};

// this was needed for `appendChild` as `document.body` does not exist when this script starts
// not necessarily required for other functions, so you could call your `overwriteFoobar()` function
// from the root of the script without using `MutationObserver`
// https://stackoverflow.com/a/26324641/2640621
var observer = new MutationObserver(function() {
  if (document.body) {
    overwriteAC();
    observer.disconnect();
  }
});
observer.observe(document.documentElement, {childList: true});

【讨论】：