Comments on: Reading cookies the regular expression way

By: Lea Verou

Lea Verou — Sat, 16 Jan 2010 21:01:59 +0000

Have you actually tested that or are you just guessing?
I think in most cases regular expressions are actually faster than string manipulation. Most JS frameworks even use them for simple case-insensitive string comparisions.

By: H

Fri, 15 Jan 2010 18:17:07 +0000

There’s a reason actually that a JS developer always avoids regular expressions, and that is code speed and performace. Perhaps it won’t make much of a difference on your rig, but it all adds up making a website slower and slower on a netbook or older computer.

By: Lea Verou

Lea Verou — Sun, 06 Dec 2009 12:14:50 +0000

You guys are both sooooo right!

Kangax, I can’t believe I missed that, gosh!

Post updated. Thank you both!!

By: kangax

kangax — Sun, 06 Dec 2009 03:58:40 +0000

It would probably make sense to escape name against regex meta characters. Looking at RFC2109, I see that characters allowed in cookie attribites are non-whitespace non-special ones (as defined in HTTP/1.1). HTTP/1.1 (RFC2068), in its turn, lists a set of special chars that appear to be not fully identical to special chars of regular expressions in ECMAScript. So… escaping names would be a good idea

And in fact, I just tried it in console:

document.cookie = ‘foo|bar=baz’;
readCookie(‘foo|bar’); // “undefined”

document.cookie = ‘foo*bar=baz’;
readCookie(‘foo*bar’); // null

PPK’s `readCookie` returns proper “baz” in both cases (not saying that we should start using his solution now, just that we could do better with regex-based variant; say add this to a function — `name = name.replace(/([.*+?^=!:${}()|[\]\/\\])/g, ‘\\$1′);`)

By: James

James — Fri, 04 Dec 2009 23:58:01 +0000

Surely, the regular expression match will always return either null or the result array (and a match’s length will never be zero). So, can’t you simply return:

match && unescape(match[1])

I agree with you about PPK’s solution being a bit too verbose; PPK’s JavaScript, IMO, is not his forte. He’s always been a DOM Guru in my books… His JS never really impressed me.

Regular expressions FTW