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

Here's a example:

s/,([^,]+),\1/,$1/g;

Perl regex substitution, but should be convertible to JS-style by anyone who knows the syntax.