Removing duplicates in a comma-separated list with a regex?

Question

I\'m trying to figure out how to filter out duplicates in a string with a regular expression, where the string is comma separated. I\'d like to do this in javascript, but I\

Answer 1

If you insist on RegExp, here's an example in Javascript:

"1,1,1,2,2,3,3,3,3,4,4,4,5".replace (
    /(^|,)([^,]+)(?:,\2)+(,|$)/ig, 
    function ($0, $1, $2, $3) 
    { 
        return $1 + $2 + $3; 
    }
);

To handle trimming of whitespace, modify slightly:

"1,1,1,2,2,3,3,3,3,4,4,4,5".replace (
    /(^|,)\s*([^,]+)\s*(?:,\s*\2)+\s*(,|$)\s*/ig, 
    function ($0, $1, $2, $3) 
    { 
        return $1 + $2 + $3; 
    }
);

That said, it seems better to tokenise via split and handle duplicates.