Javascript regex for tag in comments

Question

I've been working on a web app in which users can comment and reply to comments, this uses a tagging system. The users are being tagged by their name which can contain more words so I've decided to mark the takes like this:

&&John Doe&&

So a comment might look like this:

&&John Doe&&, are you sure that &&Alice Johnson&& is gone?

I'm trying to write a regex to match use in a string.replace() javascript function, so the regex must match every single tag in the string.

So far I have:

^&&.+{2, 64}&&$

This isn't working so I'm sure something is wrong, in case you didn't understand what I meant, the regex from above is supposed to match strings like this:

&&anythingbetween2and64charslong&&.

Thanks in advance!

Are there some edge cases you want to consider? Like & inside a name or escaping mechnisms? Otherwise just go by &&.{2,64}?&& — Sebastian Proske
– Sebastian Proske, Commented Feb 4, 2017 at 19:52
No, the usernames will contain only alphabetic characters, whitespaces and apostrophes. — Nelutu Fona
– Nelutu Fona, Commented Feb 4, 2017 at 19:54

user1636522 · Accepted Answer · 2017-02-04 19:53:51Z

3

(.*?)&& means "everything until &&" :

var before = document.getElementById("before");
var after = document.getElementById("after");
var re = /&&(.*?)&&/g, b = "<b>$1</b>";

after.innerHTML = before.textContent.replace(re, b);

<p id="before">&&John Doe&&, are you sure that &&Alice Johnson&& is gone?</p>
<p id="after"></p>

answered Feb 4, 2017 at 19:53

user1636522

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2 Comments

dude Over a year ago

Don't use innerHTML as it'll destroy events and triggers regeneration of the DOM. Instead, use something like mark.js, e.g. new Mark(document.getElementById("before")).markRegExp(/&&(.*?)&&/g);

user1636522 Over a year ago

You are right @dude, I use it for demo purpose only, but it can be misleading indeed :-)

TheRealMrCrowley · Accepted Answer · 2017-02-04 19:54:00Z

0

try &{2}.{2,64}&{2}

if you want to get the match in between add parentheses for the match group

&{2}(.{2,64})&{2}

right now your are only checking strings where the entire line matches

the ^ character means beginning of line the $ character means end of line \A means beginning of entire string \Z means end of entire string

answered Feb 4, 2017 at 19:54

TheRealMrCrowley

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Comments

jetpackpony · Accepted Answer · 2017-02-04 20:00:04Z

0

Here's what you need:

str.match(/&&.{2,64}?&&/g)

you need to remove ^ and $ from the start and the end since they match the start and the end of the string.
add a /g flag at the end so all the matches will be matched
? after the {} makes the match non-greedy, so it will match the shortest possible string between "&&" instead of the longest (will give you "&&John Doe&&" instead of "&&John Doe&&, are you sure that &&Alice Johnson&&")

Read up on greediness: Repetition with Star and Plus

answered Feb 4, 2017 at 20:00

jetpackpony

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Comments

Bahadir Tasdemir · Accepted Answer · 2017-02-04 20:27:00Z

-1

This regex will match any Unicode letter between && signs:

str.match(/\&\&[\p{L}\p{N}]+(?:\s+[\p{L}\p{N}]+)*\&\&/g);

Here,

\p{L} --> Any unicode letter, the names can be any language and letter
\p{N} --> Any unicode digit
[\p{L}\p{N}]+ --> A word constructed with unicode letters or digits
\s+ --> Gaps between words, max 3 length
[\p{L}\p{N}]+(?:\s+[\p{L}\p{N}]+)* --> All word groups

edited Feb 4, 2017 at 20:27

answered Feb 4, 2017 at 20:01

Bahadir Tasdemir

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13 Comments

Nelutu Fona Over a year ago

Now this looks like a complete approach, thank you, sir!

Bahadir Tasdemir Over a year ago

Yeah, you know names are all from different kinds of languages so you have to use the unicode match-case for the regex pattern, updated it

Wiktor Stribiżew Over a year ago

This will only work with XRegExp. Native JS regex engine does not support Unicode property classes.

Bahadir Tasdemir Over a year ago

So @NelutuFona you gotta find a server-side approach, because I am sure you will face with this problem somehow

Nelutu Fona Over a year ago

Yea, right now I need to buld a server-side approach for this(strictly for one name, used in URL), so basically I need a regex that will work with php 7 and will match any name, no shorter than 2 characters and no longer than 64

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