Javascript正则表达式中[^]的含义是什么? [英] What is meaning of [^] in Javascript regexps?

问题描述

[^ a] 表示除 a 之外的任何其他字符，但是 [^] 的含义是什么(没有以下字符)吝啬的?正如-在诸如 [-] 这样的情况下失去了字符范围的含义一样，我假设 [^] 将与插入符号匹配.我花了很长时间调试这个问题，才发现至少在Chrome 19中它看起来可以匹配任何东西，换句话说，等同于..是否有适用的规范或预期的行为?

[^a] means any character other than a, we know, but what does [^] (with no following characters) mean? Just as - loses its meaning of character range in cases such as [-], I assumed that [^] would match the caret. I spent way too long debugging this problem, only to find out that at least in Chrome 19 it appears to match anything--in other words, be equivalent to .. Is there a spec applicable here or what is the expected behavior?

是的，我知道我可以并且应该使用 [\ ^] .这个问题更多的是病态好奇心.

Yes, I'm aware that I can and probably should use [\^]. This question is more in the nature of morbid curiosity.

推荐答案

根据JavaScript规范(ES3和ES5)， [^] 与任何单个代码单元匹配，与相同[\ s \ S] ， [\ 0- \ uffff] ，(.| \ s)(请勿使用；与其他语言不同，与.的不同之处在于，该点与四个换行符( \ r ， \ n ， \ u2028 和 \ u2029 ).

According to the JavaScript specification (ES3 and ES5), [^] matches any single code unit, the same as [\s\S], [\0-\uffff], (.|\s) (don't use that; unlike the others, it relies on backtracking), etc. The difference from . is that the dot doesn't match the four newline code points (\r, \n, \u2028, and \u2029).

我不建议使用 [^] 或 [] ，因为它们不能跨浏览器一致地工作，并且它们会阻止您的正则表达式在其他浏览器中工作编程语言.IE< = 8和更早版本的Safari对空字符类使用传统的(非JavaScript)正则表达式行为.较旧的Opera版本会逆转正确的JavaScript行为，因此 [] 可以匹配任何代码单元，而 [^] 则永远不会匹配.传统的正则表达式行为是，字符类中的前导，未转义的] 被视为文字字符，并且不结束字符类.

I don't recommend using [^] or [], because they don't work consistently cross-browser, and they prevent your regexes from working in other programming languages. IE <= 8 and older versions of Safari use the traditional (non-JavaScript) regex behavior for empty character classes. Older versions of Opera reverse the correct JavaScript behavior, so that [] matches any code unit and [^] never matches. The traditional regex behavior is that a leading, unescaped ] within a character class is treated as a literal character and does not end the character class.

如果您使用 XRegExp 库，则 [] 和 [^]可以正常且始终跨浏览器运行.XRegExp还添加了 s (又名dotall或singleline)标志，该​​标志使点匹配任何代码单元(与正确遵循JavaScript规范的浏览器中的 [^] 相同).).

If you use the XRegExp library, [] and [^] work correctly and consistently cross-browser. XRegExp also adds the s (aka dotall or singleline) flag that makes a dot match any code unit (the same as [^] in a browser that correctly follows the JavaScript spec).

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