Proposal for exact matching and matching at a position in RegExp

Kam Kasravi kamkasravi at
Tue Feb 9 07:34:47 PST 2010

Hi Andy

I had mentioned to Brendan at the last TC39 that you had ported narcissus and had observed the cost of match.
There is a new global regexp parameter called 'y' which prevents the copy from occurring.
I've taken a look at narcissus and made some edits adding y to match. Both Brendan and Bob Clary
have advised on how to get the changes into mercurial on mozilla if you are not a developer within mozilla.
I can forward you these emails and we could review respective changes if you would like and its ok with 
mozilla. The mozilla bug id is


From: Andy Chu <andy at>
To: es-discuss <es-discuss at>
Sent: Mon, February 8, 2010 11:46:06 PM
Subject: Re: Proposal for exact matching and matching at a position in RegExp

On Wed, Jan 27, 2010 at 10:03 PM, Andy Chu <andy at> wrote:
> (The original message was held up in spam moderation for awhile)
> Here is an addendum, after it was pointed out to me that this issue
> has come up before:
> Basically the proposal is to add parameters which can override the
> internal state of the RegExp.

Does anyone have any comments on this?

Can I put it in a place where it will be considered for the next
ECMAScript?  The overall idea seems relatively uncontroversial since
it was already implemented by Mozilla (for the exact same reason).  I
have proposed a specific API enhancement too.

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