JavaScript/ECMAScript是常规语言吗? [英] Is JavaScript/ECMAScript a Regular Language?

问题描述

我已经尝试了一些Google搜索，但无法提出解决此问题的任何文章/先前的问题.原因是我与某人之间存在一个小争议，涉及使用输入验证来拒绝可能的XSS.我知道HTML不是一种常规语言，但是我不能对JavaScript提出如此强烈的要求.

I've tried a few google searches, and I cannot come up with any articles/previous questions that address this. The reason is a minor dispute I'm having with someone about using input validation to reject possible XSS. I know for a fact that HTML isn't a regular language, but I can't make that argument quite as strongly for javascript.

我检查了此链接:

http://www.dlsi.ua.es/~ mlf/nnafmc/pbook/node46.html

我想出了这一点:由于html中的标签可以无限嵌套，因此这是为什么HTML不是常规语言的直观概念.通过扩展，由于您可以使用{}无限嵌套JavaScript代码块，因此javascript也不是常规语言.

And I've come up with this: Since tags in html can be infinitely nested, that's an intuitive notion as to why HTML is NOT a regular language. By extension, since you can infinitely nest blocks of JavaScript code with {}, then javascript too is NOT a regular language.

我希望看到一个更正式的演讲，以支持或反对这种非正式的主张.甚至可能是关于编程语言中的正则表达式扩展的讨论，这些扩展使也许无需编写解析器就可以执行此类操作.

I'd like to see a more formal presentation either for or against this informal proposition. Or maybe even a discussion about regex extensions in programming languages that perhaps make it possible to do this kind of thing without writing a parser.

推荐答案

实际上，JavaScript不是一种常规语言，事实可以证明，必须根据您的直觉建议平衡括号.

Indeed, JavaScript is not a regular language, which can be proved with the fact that braces must be balanced as your intuition suggested.

抽引引语是证明语言不正常的有用工具.您可以使用它来证明如果JavaScript是常规的，则类似

A useful tool for demonstrating that languages are not regular is the Pumping Lemma. You can use it to demonstrate that if JavaScript was regular, some sequence like

function(){ function() { function(){ ... function () {

(其中{不匹配)在被某个前缀和后缀包围时可以重复任意次，这显然与必须匹配花括号的事实相矛盾.

(in which { are not matched) could be repeated any number of times when surrounded by a certain prefix and suffix, which is in obviously in contradiction with the fact that curly braces must be matched.

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