regex for javascript regular expressions

Question

I need to parse some JavaScript code in C# and find the regular expressions in that.

When the regular expressions are created using RegExp, I am able to find. (Since the expression is enclosed in quotes.) When it comes to inline definition, something like:

var x = /as\/df/;

I am facing difficulty in matching the pattern. I need to start at a /, exclude all chars until a / is found but should ignore \/.

I may not relay on the end of statement (;) because of Automatic Semicolon Insertion or the regex may be part of other statement, something like:

foo(/xxx/); //assume function takes regex param

If I am right, a line break is not allowed within the inline regex in JavaScript to save my day. However, there the following is allowed:

var a=/regex1def/;var b=/regex2def/;
foo(/xxx/,/yyy/)

I need regular expression someting like /.*/ that captures right data.

you can use regexhero.net/tester to find regexp for particular text — rt2800
– rt2800, Commented Sep 25, 2013 at 8:19
You want a regular expression that matches... regular expressions? — Simon Whitehead
– Simon Whitehead, Commented Sep 25, 2013 at 8:20
@SimonWhitehead: Yes I need regex to capture jaavscript regexps. Tim: I have no issues with modifiers as of now, but it would be an addon — Krishna Sarma
– Krishna Sarma, Commented Sep 25, 2013 at 8:28

georg · Accepted Answer · 2013-09-25 08:55:21Z

3

You cannot reliably parse programming languages with regular expressions only. Especially Javascript, because its grammar is quite ambiguous. Consider:

a = a /b/ 1
foo = /*bar*/ + 1
a /= 5 //.*/hi

This code is valid Javascript, but none of /.../'s here are regular expressions.

In case you know what you're doing ;), an expression for matching escaped strings is "delimiter, (something escaped or not delimiter), delimiter":

 delim ( \\. | [^delim] ) * delim

where delim is / in your case.

answered Sep 25, 2013 at 8:55

georg

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Krishna Sarma · Accepted Answer · 2013-09-25 08:31:02Z

0

After several trials with RegexHero, this seems working. /.*?[^\\]/. But not sure if I am missing any corner case.

answered Sep 25, 2013 at 8:31

Krishna Sarma

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Tim Pietzcker Over a year ago

This definitely fails. Consider /\\/.

Tim Pietzcker · Accepted Answer · 2013-09-25 08:58:27Z

0

How about this:

Regex regexObj = new Regex(@"/(?:\\/|[^/])*/");

Explanation:

/       # Match /
(?:     # Non-capturing group:
 \\     # Either match \
 /      # followed by /
|       # or
 [^/]   # match any character except /
)*      # Repeat any number of times
 /      # Match /

edited Sep 25, 2013 at 8:58

answered Sep 25, 2013 at 8:21

Tim Pietzcker

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5 Comments

Krishna Sarma Over a year ago

When I checked with RegexHero, this expression yields no results

Jerry Over a year ago

@Tim you probably meant \/(?:\\\/|[^\/])*\/ (no delimiters in C#)

Tim Pietzcker Over a year ago

@Jerry: Ah, I read JavaScript and thought he needs a JavaScript regex. In .NET, it's easier :)

Jerry Over a year ago

@Tim Oh I forgot to remove the extra backslashes for the escaping x3

Tim Pietzcker Over a year ago

@KrishnaSarma: I misread your question; I thought you needed a JavaScript regex, not a .NET one. Edited.

kaushik0033 · Accepted Answer · 2013-09-25 09:15:44Z

0

I think that this may help you var patt=/pattern/modifiers;

•pattern specifies the pattern of an expression •modifiers specify if a search should be global, case-sensitive, etc.

answered Sep 25, 2013 at 9:15

kaushik0033

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