为什么}！{在JavaScript控制台中导致False? [英] Why does }!{ result in False in a JavaScript console?

问题描述

如果将}！{放在Chrome的JavaScript控制台中，结果将得到 false .

If you put }!{ in your JavaScript console in Chrome, as a result you will get false.

为什么我们没有收到错误消息?

Why don't we get an error?

推荐答案

此行为的原因是因为Chrome使用另一段代码将您输入到控制台中的所有内容包装起来.

The reason for this behaviour is because Chrome wraps anything you enter into the console with another piece of code.

(在撰写本文时)包装的代码如下:

The code it wraps with (at the time of writing) is as follows:

with ((window && window.console && window.console._commandLineAPI) || {}) {
    // Your code here.
}

输入}！{将关闭代码块大括号，并在最后创建一个新的(取反)对象.

Entering }!{ closes the code block brace, and makes a new (negated) object at the end.

您可以在控制台中看到自己的！{} 返回 false .

As you can see for youself in the console !{} returns false.

我经过一个漫长的调查过程来找到答案，下面保留了我的原始评论

I went through quite a lengthy investigative process to find the answer to this, my original comments are preserved below

原始答案:

只是一种理论；我想象在控制台中输入的代码在函数内部被调用

Just a theory; I imagine the code entered in the console being called inside a function

函数execUserCode(){代码}

您正在做的是创建

function execUserCode(){}！{}

控制台返回的最后一个结果实际上是！{} = false

The console is returning the last result, which is actually !{ } = false

有关此怎么可能是错误的许多评论.我同意.这只是一个理论.

Lots of comments about how this is probably wrong. I agree. It's just a theory.

我喜欢这些谜题，所以我对Chromium来源进行了深入的研究，这对我来说有点多了，但是我会留下一些建议，以防其他人被刺伤.

I like these kind of puzzles so I had a dig through the Chromium source, it's a bit much for me but I'll leave some pointers in case anyone else has a stab.

JS控制台称为检查器"，可以在这里找到:

The JS console is called the "inspector" and can be found here:

chromium/src/third_party/WebKit/Source/WebCore/inspector/

我一直在查看 inspector/front-end/ConsoleView.js ，我想我发现了执行用户代码的位置.

I've been looking at inspector/front-end/ConsoleView.js and I think I found a bit of where the user code is executed.

evaluateUsingTextPrompt: function(expression, showResultOnly)
{
    this._appendCommand(expression, this.prompt.text, false, showResultOnly);
},

---

原因！

小脑波.我是在控制台中完成的

---

The reason!

Little brainwave. I did this in the console

> myEval = eval
> eval = function(str) { console.log(str); myEval(str) }
> }!{

结果:

with ((window && window.console && window.console._commandLineAPI) || {}) {
}!{
}

我很近，但是现在我们有了答案:)

I was close, but now we have the answer :)

该代码是在当前第440行附近的 chromium/src/third_party/WebKit/Source/WebCore/inspector/InjectedScriptSource.js 中生成的.

The code is generated in chromium/src/third_party/WebKit/Source/WebCore/inspector/InjectedScriptSource.js currently around line 440.

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