r2p is a Javascript Regex to PEG converter. It parses regexes using PEGjs with grammar rules inspired by Kevin Mehall's regexp grammar and converts them to PEGjs-compatible grammar using the method described in Marcelo Oikawa, Roberto Ierusalimschy and Ana Lucia de Moura's "Converting regexes to Parsing Expression Grammars".
You need PEGjs to build the regular expression parser used by r2p. If you don't have it already installed globally, you can install it locally using npm install in the source directory. You can then run make to build the parser.
You need both regexParser.js and converter.js to use r2p. You can then call the r2p function, passing it the regular expression to convert as a string.
For now the parser only supports a subset of JS regular expressions. Lookahead ((?=x), (?!x)) and lookbehind ((?<x), (?<!x)) assertions, numeric (x{n,m}) and (un-)greedy (x*?, x*+) quantifiers as well as non-capturing groups ((?:x)) are not recognized by the parser. Capturing groups are only used to group expressions together and will not be translated into separate non-terminals in the output grammar. You may also have issues with some escape sequences. Hopefully those will be fixed in a future release.
r2p is public domain. Do whatever you please with it, but do not hesitate to drop a note if you find it interesting.