I'm processing a comma delimited string and need to *ALL* replace missing values with '0's. Leading and/or trailing ','s denote missing values. For example:

 The string ",,2,3,,,4," becomes "0,0,2,3,0,0,4,0" 

Note that there are missing values at BOTH the beginning AND the end of the input string.

Surprisingly I did not find any online examples of this - if someone has a solution to this it would make a good addition to a regexp library.

My knowledge of regexps is limited  so I'm wondering if the replacement operation can be done in a single regexp pass. (I was able to do in 2 passes with the following code, however I'm wondering if there is  better approach).

             strIn= ",,2,3,,,4,"
             pattern:RegExp = /,(?=[,])|,$/g;            //handles all but the first missing  '0 ' - gets:  ",0,0,2,3,0,0,4,0"
             strOut: =(strIn.replace(pattern,",0"));
            //Reset Regexp Pattern Call regexp again to handle leading ',' at BOL
            pattern = /^,/g;            
            strOut=(strOut.replace(pattern,"0,"));    // Note the replace pattern is different                                

TIA,

Patrick

Raw Match Pattern:
(?<![^,]),|(?<=,)$

Raw Replace Pattern:
0$0

If you are on a platform that doesn't support (?<!) or (?<=) then the above pattern will not work for you.  In that case you may need to use a matching pattern as below:

Raw Match Pattern:
^(?=,)|,(?=,|$)

Raw Replace Pattern:
${0}0

Note that the ${0} is the syntax in PHP required for the replacement referencing $0 group while following with another number, modify for your platform as required.