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I have issues with matching a string with regexp in JS. I can use this:

/"[^"]*?"/g

in this string:

" this is a string "

but I can not use that in this:

" this is a \"string\" "

how can i fix that? thanks.

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  • 1
    It would probably be easier if you told us what it's supposed to match specifically ? Commented Jun 8, 2015 at 18:22
  • 1
    Please provide more information about your problem. What exactly do you mean by "use this ... in this string"? What is the expected outcome? Commented Jun 8, 2015 at 18:22
  • Are the quotes in your question literally part of the string? i.e., when you write " this is a string ", are you expressing an 18-character or 20-character string? Are you using literal notation (where / starts an escape sequence) or the actual character-for-character values present in the string (where a / is just a / character)? Commented Jun 8, 2015 at 18:24
  • I want match strings in a string. I mean I want to match those strings with a regular expression. I want to find anything between " and " but not \" . Commented Jun 8, 2015 at 18:26
  • Do you want to match empty string also like "" ? Commented Jun 8, 2015 at 18:34

3 Answers 3

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If i understand correct, what you want to do is test is a string is in correct format? so no premature string endings?

If that is the case you could use /"(?:[^"\\]|\\.)*"/g

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6 Comments

This is probably closer to what he needs, but I don't think he realizes that. A faster way is "[^"\\]*(?:\\.[^"\\]*)*"
@sln So why use such complicated regex when "(.*)" can does the same?
@Kasra - Its not complicated, its the standard unrolled-loop method. Its 3-5 times faster than the alternation method.
thanks. and finally this is working even better: "(?:[^"\\]|\\.)*"|'(?:[^'\\]|\\.)*'
Now test this solution with \"a\" "b"
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[^\\]?(".*?[^\\]")

You can try something like this.You will need to grab the group or capture and not match.See demo.

https://regex101.com/r/nS2lT4/30

or

(?:[^\\]|^)(".*?[^\\]")

See demo.

https://regex101.com/r/nS2lT4/31

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@moisrex did this fail in nay case?
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In that case you shouldn't use [^"]* also you don't need none-greedy you can use following regex for matching all between 2 quote :

/"(.*)"/g

Demo

And if you want to match anything between " you can simply use a word character matcher with white-space matcher within a character class with a global modifier :

/[\w\s]+/g

Demo

As another way you can use a negative look-behind :

/(?<!\\)"(.*?)(?<!\\)"/
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4 Comments

@moisrex Its negative look behind and will match string that not preced by pattern after ?<! read more regular-expressions.info/lookaround.html
unfortunately look-behind does not supports in JavaScript. but thanks for mentioning that. I learned a lot today.
Using (?<!\\)" prevents quotes preceded by a backslash, but it does in this situation too: \\" where the quote is preceded by two (or an even number) of backslashes. In these cases the quote is no more escaped.
@CasimiretHippolyte So in this case that you are talking about it can has a lot of scenarios. It's just a recipe for this case!

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