具有右方括号字符的javascript match方法

Question

How can I use a closing square bracket as a character in a javascript regular expression?

"Acb[".match('[\(, \), \[]')

returns:

["["]

But when I add the closing square bracket as a character it does not work :

"Acb[".match('[\(, \), \[, \]]')
null


"Acb]".match('[\(, \), \[, \]]')
null

Answer 1

"Acb]".match(/[\\(, \\), \\[, \\]]/) returns ["]"] . You should use / instead of a quotation mark to denote a regex to avoid problems with escaping

You also dont need to escape most of those characters. "Acb]".match(/[()[, \\]]/) will match (, ), [, ], a comma, or a space

Info on character classes can be found here

Answer 2

@wolffer-east's answer is correct. I'm posting just to explain why his/her answer works.

According to MDN , the argument to String.prototype.match can be a string rather than a regex:

Parameters

regexp

A regular expression object. If a non-RegExp object obj is passed, it is implicitly converted to a RegExp by using new RegExp(obj).

So it's not immediately obvious why using slashes to delimit the regex works, while using quotes doesn't. The reason is that the two delimitation forms treat backslash-escaping differently. When you write

"Acb[".match('[\(, \), \[, \]]')

The quotes apply the backslash-escaping first, before any regex is created. Since backslash-parentheses and backslash-bracket are not special escape sequences, they translate to just parentheses and bracket, respectively. Thus this:

'[\(, \), \[, \]]'

is equivalent to this:

'[(, ), [, ]]'

It's only after that that the RegExp constructor is invoked. At this point the closing bracket is no longer escaped, and is treated as the ending marker for the character class rather than a character within the class. You can avoid this by escaping the backslash itself:

"Acb[".match('[\(, \), \[, \\]]')

--

It also seems that you're using commas to separate the characters in your character class - this is unnecessary, no separator is required. A simpler expression would thus be:

"Acb[".match(/[()[\]]/)

or

"Acb[".match('[()[\\]]')