How come this RegExp doesn't work when passed in as a string?

Question

Chrome 9.0.597.83 beta on Ubuntu 10.10:

enter image description here

As you can see, the pattern doesn't work when passed in as a string, but works fine when passed in as a RegExp object. Why is this? I need to be able to pass it in as a string so that I can manipulate it before performing the match.

_{Note: I just posted a question very similar to this... and thought I was doing something wrong and deleted the question. Then when I tried something slightly different, I got the problem again.}

Now I'm getting the problem too, but only with "e c".

BoltClock
– BoltClock

2011-02-06 22:26:12 +00:00
Commented Feb 6, 2011 at 22:26 — BoltClock
– BoltClock, Commented Feb 6, 2011 at 22:26
@Bolt: Yeah, me too now.

Nathan Osman
– Nathan Osman

2011-02-06 22:26:54 +00:00
Commented Feb 6, 2011 at 22:26 — Nathan Osman
– Nathan Osman, Commented Feb 6, 2011 at 22:26

lonesomeday · Accepted Answer · 2011-02-06 22:26:42Z

5

The problem is with the backslash \. This is escaping the W character. In a string, \W evaluates to W. You need to escape the backslash:

"e c".match(new RegExp('(?:^|\\W)c(?:\\W|$)'))

answered Feb 6, 2011 at 22:26

lonesomeday

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2 Comments

Nathan Osman Over a year ago

[Facepalm] Why didn't I think of that? Good job.

lonesomeday Over a year ago

@George It took doing console.log(new RegExp('(?:^|\W)c(?:\W|$)')) to make me figure it out!

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