检查是否已在JavaScript中覆盖全局属性/函数 [英] Check if a global property/function has been overwritten in JavaScript

问题描述

JavaScript可以轻松覆盖全局对象的属性和功能。我想找到一种方法来检查全局属性的原始版本是否已被替换。

JavaScript makes it easy to overwrite properties and functions of the global object. I'd like to find a way to check if the original version of a global property has been replaced.

考虑有人将其放入HTML：

Consider someone putting this in their HTML:

<script type="text/javascript">
    window.encodeURIComponent = eval;
</script>
<script type="text/javascript" src="myscript.js"></script>

如果myscript.js在某处调用encodeURIComponent函数，它现在将表现得不可预测。那么，如果有人在我使用之前覆盖了该函数，我可以检查一下myscript.js吗？

If myscript.js calls the encodeURIComponent function somewhere, it will now behave unpredictably. So is there a way I can check inside myscript.js if someone has overwritten that function before I use it?

推荐答案

唯一我所知道的是一种直接的方法，分析函数的字符串表示。通常，代码

The only thing I know is a straightforward approach with analysis of string representation of the function. Normally, the code

window.encodeURIComponent.toString()

应该产生这样的东西：

function encodeURIComponent() { [native code] }

可以很容易地解析密钥信息 function encodeURIComponent 。

which can be easily parsed for key info function encodeURIComponent.

如果函数被 eval 覆盖，就像在你的例子中一样，你' ll get：

If the function was overwritten by eval, as in your example, you'll get:

function eval() { [native code] }

通常，对于检查窗口属性，您可以创建一个假的iframe并比较 window。[property] .toString（） with iframe.contentWindow。[property] .toString（）。如果比较为 false ，则该属性已更改。

In general, for checking window properties, you can create a fake iframe and compare window.[property].toString() with iframe.contentWindow.[property].toString(). If the comparison gives false, the property has been changed.

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