Javascript regexp文字和构造函数之间的差异 [英] Differences between Javascript regexp literal and constructor

问题描述

我们最近有一个错误，在一位开发人员将一个RegExp文字改为构造函数调用后，我想知道为什么会有任何差异。
具体代码是

We recently had a bug, after a fellow developer changed a RegExp literal into a constructor call, and I was wondering why there is any difference at all. The exact code was

var parts = new RegExp("/rt:([^@]+)@(\d+)/").exec(tag);

vs原始

var parts = /rt:([^@]+)@(\d+)/.exec(tag);

当标签是，例如 rt：60C1C036-42FA-4073-B10B-1969BD2358FB @ 00000000077 ，第一个（错误）调用返回 null ，而第二个一个返回 [rt：60C1C036-42FA-4073-B10B-1969BD2358FB @ 00000000077，60C1C036-42FA-4073-B10B-1969BD2358FB，00000000077]

When tag is, for example rt:60C1C036-42FA-4073-B10B-1969BD2358FB@00000000077, the first (buggy) call returns null, while the second one returns["rt:60C1C036-42FA-4073-B10B-1969BD2358FB@00000000077", "60C1C036-42FA-4073-B10B-1969BD2358FB", "00000000077"]

毋庸置疑，我还原了这一变化，但我想知道为什么首先会出现这样的差异。

Needless to say, I reverted the change, but I'd like to know why is there such a difference in the first place.

推荐答案

有两个问题：

/ 不表达式的一部分。它们是分隔符，标记正则表达式文字。如果你使用 RegExp ，则必须删除它们，否则它们按字面意思匹配斜杠。

The / are not part of the expression. They are delimiters, marking a regex literal. They have to be removed if you use RegExp, otherwise they match a slash literally.

其次，反斜杠是字符串文字中的转义字符。要为表达式创建文字 \ ，您必须在字符串中对其进行转义。

Secondly, the backslash is the escape character in string literals. To create a literal \ for the expression, you have to escape it in the string.

因此，相当于：

new RegExp("rt:([^@]+)@(\\d+)")

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特别是逃避使得表达更加困难如果你想使用 RegExp ，写。实际上只有在想要动态创建表达式时才需要它，例如，如果要包含存储在变量中的文本。如果你有一个固定的表达式，文字 /.../ 更容易编写，更简洁。

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Especially the escaping makes expression a bit more difficult to write if you want to use RegExp. It is actually only needed if you want to create expression dynamically, that is, if you want to include text stored in a variable for example. If you have a fixed expression, a literal /.../ is easier to write and more concise.

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