正则表达式替换匹配的组内容？

Question

I have the regex :

(a+)(,)(b+)

which is anallyzing the string : aaaa,bbb

It is very important for me to keep the group $1 , $2, $3.

I need a Regex usage( only , no Js , c# etc) which will giv me this :

kkkk,ppp

flow :

1) emit group1  , group2  , group3
2) keep the $2 group
3)replace the 'a' to 'k' ( as many as 'a'.count)
3)replace the 'b' to 'p' ( as many as 'b'.count)

edit

I dont have problem to string.replace(regexp/substr,newstring) in Js

But I dont want any loops or someting like that.

Answer 1

Try this :

str.replace(
   new RegExp("([ab]+)", "g"),  
   // Here, we are passing in a nameless function as the parameter for
   // the "replace" argument of the String Replace method. It uses the $1
   // to refer to the grouping of a or b.
   function($1){
      if ($1.charAt(0) == "a"){
      // replace with k
      return( $1.replace(/./g, "k") );
      } else {
      // replace with p
      return( $1.replace(/./g, "p") );
      }
   }
)

Adjust it to your own needs.

Answer 2

Regular expressions are a pattern matching mechanism. What you are asking for is pattern replacement. This is possible by additional language constructs that differ from language to language, but not by regex itself. As you expressly exclude any language specifics, there is no answer to your question.

Edit:

Ok, now you have edited your question and allow language specific solutions. See Ed's answer.