Odd RegEx request for Javascript

Question

I'm having trouble with a certain RegEx replacement string for later use in Javascript.

We have quite a bit of text that was stored in a rather odd format that we aren't allowed to fix. But we do need to find all the "network path" strings inside it, following these rules:

A. The matches always start with 2 backslashes.
B. The matching characters should stop as soon as it hits a first occurrence of any 1 of these:

A < character
A space
A line feed
A carriage return
A & character
A literal "\r" or "\n" string (but only if occurring at end of line)

We "almost" have it working with /\\\\[^ &<\s]*/gi as shown in this RegEx Tester page: https://regex101.com/r/T4cDOL/5

Even if we get it working, the RegEx has to be even futher "escape escaped" before putting on our Javascript code, but that's also not working as expected.

3 revs · Accepted Answer · 2020-07-14 16:36:43Z

2

From your example, it seems you literally have a backslash followed by an n and a backslash followed by an r (as opposed to a newline or carriage return), which means you can't only use a negated character class (since you need to handle a sequence of two characters). I'd use a positive lookahead to know where to stop, so I can use an alternation for that part.

You haven't said what parts of those strings should match, so I've had to guess a bit, but here's my best guess (with useful input from Niet the Dark Absol):

const rex = /\\\\.*?(?=[ &<\r\n]|\\[rn](?:$| ))/gmi;

That says:

Match starting with \\
Take everything prior to the lookahead (non-greedy)
Lookahead: An alternation of:
- A space, &, <, carriage return (\r, character 13), or a newline (\n, character 10); or
- A backslash followed by r or n if that's either at the end of a line or followed by a space (so we get the \nancy but not the \n after it).

Updated regex101

You might want to have more characters than just a space after the \r/\n. If so, make it a character class (and/or use \s for "whitespace" if that applies):

const rex = /\\\\.*?(?=[ &<\r\n]|\\[rn](?:$|[ others]))/gmi;
// −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−^^^^^^^^^

edited Jul 14, 2020 at 16:36

community wiki

3 revs
T.J. Crowder

Sign up to request clarification or add additional context in comments.

8 Comments

SusanSuzy Over a year ago

I added some more 'example text' where your idea ALMOST works, but not always: regex101.com/r/T4cDOL/5

Niet the Dark Absol Over a year ago

I think you should also handle the case where the match goes to the end of the string/line.

T.J. Crowder Over a year ago

@SusanSuzy - Please update your quesiton to put all of the information necessary to answer it in the question, not just linked. Be sure to show what should match. Two reasons: People shouldn't have to go off-site to help you; and links rot, making the question and its answers useless to people in the future. Please put a minimal reproducible example in the question. More: How do I ask a good question? and Something in my web site or project doesn't work. Can I just paste a link to it?

T.J. Crowder Over a year ago

@NiettheDarkAbsol - Not a bad idea, I'll add \r\n to the character class.

Niet the Dark Absol Over a year ago

regex101.com/r/T4cDOL/6 -- seems like some of the "paths" might have \n as a substring, so that token isn't always going to be a delimiter. The whole thing is awkward tbh XD

|

Collectives™ on Stack Overflow

Odd RegEx request for Javascript

1 Answer 1

8 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Related