?: in regular expression

[deepak.rathore]

Hi ,
I have seen lot of reg. expession with ?:
For dummy eg
(((XXX)ddd)ff)

The above expression is modified as
(?:(?:(XXX)ddd)ff)

Although both the above expr. gives same result. (RegExp.match() gives
same o/p), most of the places , i have seen second option.

Yes, but different matches r shown (using RegExp.exec())

Is the second expr. most efficient or in particular scenarios?

Any comments???

Thanks in advance.

[David Dorward]

de************@gmail.com wrote:

I have seen lot of reg. expession with ?:

It makes the brackets non-capturing (not a back reference)
http://www.regular-expressions.info/brackets.html

[deepak.rathore]

Thanks David

That means when i am using back reference( I suppose like \2) in reg.
exp; ?: can optimise it. Am I right ???

But is there any difference using / not using ?: when i have no back
references in reg exp.

[Thomas 'PointedEars' Lahn]

de************@gmail.com wrote:

That means
Are you referring to something?

<URL:http://jibbering.com/faq/faq_notes/pots1.html>
<URL:http://safalra.com/special/googlegroupsreply/>
when i am using back reference( I suppose like \2) in reg.
exp; ?: can optimise it. Am I right ???
For appropriate values of "optimise".
But is there any difference using / not using ?:
when i have no back references in reg exp.

Parse error.
PointedEars

[deepak.rathore]

I got the answer from David Dorward's link

http://www.regular-expressions.info/brackets.html

Thanks

[Thomas 'PointedEars' Lahn]

de************@gmail.com wrote:

I got the answer from David Dorward's link
The answer to what?
http://www.regular-expressions.info/brackets.html

(Well, I can extract meaning from read text, can you?)

Backreferences within Regular Expressions are not universally supported in
ECMAScript implementations, and they equal the previous match, not the
previous subexpression. I fail to see any optimization in using them here,
unless we are talking about specific server-side code.
PointedEars