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javascript - 停止执行 Javascript 函数(客户端)或对其进行调整

转载 作者:行者123 更新时间:2023-12-01 05:49:01 34 4
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我想停止执行站点中的一行,以便浏览器读取除该行之外的整个页面。或者浏览器可能会简单地跳过该 JavaScript 函数的执行。

或者

有没有办法我可以以某种方式调整javascript,以便javascript中的随机数生成函数不生成随机数,而是生成我想要的数字......

我无权访问托管脚本的网站,因此所有这些都需要在客户端完成。

最佳答案

Firefox 目前支持the beforescriptexecute event (自 Version 4, released on March 22, 2011 起)

随着该事件和 the // @run-at document-start directive 、Firefox 和 Greasemonkey 现在似乎在拦截特定方面做得很好 <script>标签。

这对于 Chrome+Tampermonkey 来说仍然是不可能的。对于除 Firefox+Greasemonkey 之外的任何内容,您将需要使用下面其他答案中所示的技术来编写完整的浏览器扩展。

The checkForBadJavascripts function封装了这一点。例如,假设页面有 <script>像这样的标签:

<script>
alert ("Sorry, Sucka! You've got no money left.");
</script>

您可以使用checkForBadJavascripts像这样:

checkForBadJavascripts ( [
[ false,
/Sorry, Sucka/,
function () {
addJS_Node ('alert ("Hooray, you\'re a millionaire.");');
}
]
] );

获得更好的消息。 (^_^)
有关更多信息,请参阅 checkForBadJavascripts 中的内联文档。

<小时/>

要查看完整脚本的演示,请首先访问this page at jsBin 。您将看到 3 行文本,其中两行是由 JS 添加的。

现在,install this script (View source;也在下面。)并重新访问该页面。您将看到 GM 脚本删除了一个坏标签,并用我们的“好”JS 替换了另一个标签。

<小时/>

请注意,只有 Firefox 支持 beforescriptexecute事件。它已从 HTML5 规范中删除,且未指定等效功能。

<小时/><小时/>

完整的GM脚本示例(与GitHub和jsBin相同):

给定这个 HTML:

<body onload="init()">
<script type="text/javascript" src="http://jsbin.com/evilExternalJS/js"></script>
<script type="text/javascript" language="javascript">
function init () {
var newParagraph = document.createElement ('p');
newParagraph.textContent = "I was added by the old, evil init() function!";
document.body.appendChild (newParagraph);
}
</script>
<p>I'm some initial text.</p>
</body>


使用这个 Greasemonkey 脚本:

// ==UserScript==
// @name _Replace evil Javascript
// @include http://jsbin.com/ogudon*
// @run-at document-start
// ==/UserScript==

/****** New "init" function that we will use
instead of the old, bad "init" function.
*/
function init () {
var newParagraph = document.createElement ('p');
newParagraph.textContent = "I was added by the new, good init() function!";
document.body.appendChild (newParagraph);
}

/*--- Check for bad scripts to intercept and specify any actions to take.
*/
checkForBadJavascripts ( [
[false, /old, evil init()/, function () {addJS_Node (init);} ],
[true, /evilExternalJS/i, null ]
] );

function checkForBadJavascripts (controlArray) {
/*--- Note that this is a self-initializing function. The controlArray
parameter is only active for the FIRST call. After that, it is an
event listener.

The control array row is defines like so:
[bSearchSrcAttr, identifyingRegex, callbackFunction]
Where:
bSearchSrcAttr True to search the SRC attribute of a script tag
false to search the TEXT content of a script tag.
identifyingRegex A valid regular expression that should be unique
to that particular script tag.
callbackFunction An optional function to execute when the script is
found. Use null if not needed.
*/
if ( ! controlArray.length) return null;

checkForBadJavascripts = function (zEvent) {

for (var J = controlArray.length - 1; J >= 0; --J) {
var bSearchSrcAttr = controlArray[J][0];
var identifyingRegex = controlArray[J][1];

if (bSearchSrcAttr) {
if (identifyingRegex.test (zEvent.target.src) ) {
stopBadJavascript (J);
return false;
}
}
else {
if (identifyingRegex.test (zEvent.target.textContent) ) {
stopBadJavascript (J);
return false;
}
}
}

function stopBadJavascript (controlIndex) {
zEvent.stopPropagation ();
zEvent.preventDefault ();

var callbackFunction = controlArray[J][2];
if (typeof callbackFunction == "function")
callbackFunction ();

//--- Remove the node just to clear clutter from Firebug inspection.
zEvent.target.parentNode.removeChild (zEvent.target);

//--- Script is intercepted, remove it from the list.
controlArray.splice (J, 1);
if ( ! controlArray.length) {
//--- All done, remove the listener.
window.removeEventListener (
'beforescriptexecute', checkForBadJavascripts, true
);
}
}
}

/*--- Use the "beforescriptexecute" event to monitor scipts as they are loaded.
See https://developer.mozilla.org/en/DOM/element.onbeforescriptexecute
Note that it does not work on acripts that are dynamically created.
*/
window.addEventListener ('beforescriptexecute', checkForBadJavascripts, true);

return checkForBadJavascripts;
}

function addJS_Node (text, s_URL, funcToRun) {
var D = document;
var scriptNode = D.createElement ('script');
scriptNode.type = "text/javascript";
if (text) scriptNode.textContent = text;
if (s_URL) scriptNode.src = s_URL;
if (funcToRun) scriptNode.textContent = '(' + funcToRun.toString() + ')()';

var targ = D.getElementsByTagName ('head')[0] || D.body || D.documentElement;
//--- Don't error check here. if DOM not available, should throw error.
targ.appendChild (scriptNode);
}

关于javascript - 停止执行 Javascript 函数(客户端)或对其进行调整,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24134838/

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