[whatwg] Web Forms: pattern attribute

Michel Fortin michel.fortin at michelf.com
Tue Apr 4 10:06:31 PDT 2006

Le 3 avr. 2006 à 19:33, Dean Edwards a écrit :

> Michel Fortin wrote:
>> Does that mean that a pattern attribute like "foo|bar" should  
>> translate to /^foo|bar$/ ? Wouldn't it make more sense it it was /^ 
>> (foo|bar)$/ with the parentesis?
> You have a point. Would implied parentheses cause any side effects?  
> None that I can think of...

Now that you mention it, it could. With a pattern like this:


which simply indicates that the first and the last characters must be  
the same, reference numbers won't refer to the right part. When the  
pattern get transformed to this:


it makes `\1` a reference to the whole input text (the first  
parenthesis) rather than the first character (which has become the  
second parenthesis). This is not good.

So we will need to use a non-matching group `(?: ... )` instead:


Problem solved.

Michel Fortin
michel.fortin at michelf.com

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