Why does my regular expression work in PHP but not JavaScript?

Question

I have a regex created by myself that I am currently running in PHP. Although when I merge it over to JavaScript, it refuses to work. I have also tried it in Python and it works perfectly fine.

Regex:

@[[](.[^]]+)[]][()](\d+)[)]

Testing in PHP, and working

Testing in JavaScript, and not working

have a look at the explanation - see how it differs, regex's are slightly different in different languages - make adjustments as required — Jaromanda X
– Jaromanda X, Commented Aug 16, 2015 at 0:56
Are you sure that you want to match something like: @[]User Name])1234). It seems like an odd rule for any practical purpose. — aaaaaaaaaaaa
– aaaaaaaaaaaa, Commented Aug 16, 2015 at 18:23
@eBusiness - It's actually trying to match something along the lines of @[User Name](1234). It is for a tagging system I have created so that I can convert that into a link to a users profile based on their ID by displaying their username. — Fizzix
– Fizzix, Commented Aug 18, 2015 at 2:29
@Fizzix I kind of figured that, it is just that the . and the second ) doesn't really make any sense in that context. — aaaaaaaaaaaa
– aaaaaaaaaaaa, Commented Aug 18, 2015 at 5:53

Downgoat · Accepted Answer · 2015-08-16 16:23:34Z

30

JavaScript doesn't automatically escape your ].

This will help you get a visual idea:

PCRE:

PCRE

JS:

Python:

Python

So to fix this, you need to escape the brackets

@[[](.[^\]]+)[\]][()](\d+)[)]
//      ^     ^

The best way to write this regex is to minimize the use of character classes:

@\[(.[^\]]+)\][()](\d+)\)

That's why it's good practice to escape this stuff instead of relying on quirks of the flavor.

I generated these images through regex101.

edited Aug 16, 2015 at 16:23

answered Aug 16, 2015 at 0:58

Downgoat

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4 Comments

Fizzix Over a year ago

Ohhhh, makes much more sense now. Thanks vihan, appreciate it.

Stack Exchange Broke The Law Over a year ago

Is [\]] different from just \]?

Blackhole Over a year ago

@immibis No. This regex is probably better written as @\[(.[^\]]+)\][()](\d+)\).

Fizzix Over a year ago

Thanks @Blackhole, looks a lot better. I'll run with that instead.

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