在JavaScript中，空的正则表达式模式是否定义了行为？ [英] In JavaScript, does an empty regex pattern have defined behavior?

问题描述

var pattern = /(?:)/

从我的测试来看，它似乎与一切相符。这是定义的行为吗？

From my testing, it seems to match everything. Is this the defined behavior?

推荐答案

这不能直接回答这个问题，但这里有关于该规范的说法空正则表达式：

This doesn't directly answer the question, but here's what the spec has to say about the empty regular expression:

来自 15.5.4.14 String.prototype.split（分隔符，限制）

separator可以是空字符串，空正则表达式，或者可以匹配空字符串的正则表达式。

The value of separator may be an empty String, an empty regular expression, or a regular expression that can match an empty String.

来自 7.8.5正则表达式文字

注意正则表达式文字可能不为空;字符//开始单行注释，而不是表示空的正则表达式文字。要指定空的正则表达式，请使用： /（？:) / 。

因为它是 .split（）中分隔符的可接受值，我猜它是定义的行为，作为分割每个字符的一种方式。

So given that it is an accepted value for the separator in .split(), I would guess that it is the defined behavior as a way to split on every character.

"fjeij;als#%^&é.\n isoij\t;oi`1=+-]\r".split(/(?:)/);

["f", "j", "e", "i", "j", ";", "a", "l", "s", "#", "%", "^", "&", "é", ".", "
", " ", "i", "s", "o", "i", "j", "  ", ";", "o", "i", "`", "1", "=", "+", "-", "]", "
"]

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