PO parser from http://jsgettext.berlios.de/lib/Gettext.js adapted for Node.js and modified to be more like po2json.pl

po2json.js

#!/usr/bin/env node

/*
PO parser from http://jsgettext.berlios.de/lib/Gettext.js
adapted for Node.js and modified to be more like po2json.pl
- Zach Carter <zcarter@cse.usf.edu>
*/

/*
Pure Javascript implementation of Uniforum message translation.
Copyright (C) 2008 Joshua I. Miller <unrtst@cpan.org>, all rights reserved

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU Library General Public License as published
by the Free Software Foundation; either version 2, or (at your option)
any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.
*/

var fs = require('fs');
var path = require('path');

var argv = process.argv;
var pretty = ~argv.indexOf('-p');

function parse (file) {
  fs.readFile(fs.realpathSync(file), 'utf8', function (err, data) {
    if (err) throw err;
    if (pretty) {
      var result = {};
      result[path.basename(file, '.po')] = parse_po(data);
      // perl JSON encoder uses three spaces (╯°□°）╯︵ ┻━┻
      console.log(JSON.stringify(result, null, '   '));
    } else {
      console.log(JSON.stringify(parse_po(data)));
    }
  });
}

var context_glue = "\004";

var parse_po = function(data) {
  var rv = {};
  var buffer = {};
  var lastbuffer = "";
  var errors = [];
  var lines = data.split("\n");
  for (var i=0; i<lines.length; i++) {
    // chomp
    lines[i] = lines[i].replace(/(\n|\r)+$/, '');

    var match;

    // Empty line / End of an entry.
    if (/^$/.test(lines[i])) {
      if (typeof(buffer['msgid']) != 'undefined') {
        var msg_ctxt_id = (typeof(buffer['msgctxt']) != 'undefined' &&
                          buffer['msgctxt'].length) ?
                            buffer['msgctxt']+context_glue+buffer['msgid'] :
                            buffer['msgid'];
        var msgid_plural = (typeof(buffer['msgid_plural']) != 'undefined' &&
                            buffer['msgid_plural'].length) ?
                              buffer['msgid_plural'] :
                              null;

        // find msgstr_* translations and push them on
        var trans = [];
        for (var str in buffer) {
          var match;
          if (match = str.match(/^msgstr_(\d+)/))
            trans[parseInt(match[1])] = buffer[str];
        }
        trans.unshift(msgid_plural);

        // only add it if we've got a translation
        // NOTE: this doesn't conform to msgfmt specs
        if (trans.length > 1) rv[msg_ctxt_id] = trans;

        buffer = {};
        lastbuffer = "";
      }

    // comments
    } else if (/^(#[^~]|#$)/.test(lines[i])) {
      continue;

    // msgctxt
    } else if (match = lines[i].match(/^(?:#~ )?msgctxt\s+(.*)/)) {
      lastbuffer = 'msgctxt';
      buffer[lastbuffer] = parse_po_dequote(match[1]);

    // msgid
    } else if (match = lines[i].match(/^(?:#~ )?msgid\s+(.*)/)) {
      lastbuffer = 'msgid';
      buffer[lastbuffer] = parse_po_dequote(match[1]);

    // msgid_plural
    } else if (match = lines[i].match(/^(?:#~ )?msgid_plural\s+(.*)/)) {
      lastbuffer = 'msgid_plural';
      buffer[lastbuffer] = parse_po_dequote(match[1]);

    // msgstr
    } else if (match = lines[i].match(/^(?:#~ )?msgstr\s+(.*)/)) {
      lastbuffer = 'msgstr_0';
      buffer[lastbuffer] = parse_po_dequote(match[1]);

    // msgstr[0] (treak like msgstr)
    } else if (match = lines[i].match(/^(?:#~ )?msgstr\[0\]\s+(.*)/)) {
      lastbuffer = 'msgstr_0';
      buffer[lastbuffer] = parse_po_dequote(match[1]);

    // msgstr[n]
    } else if (match = lines[i].match(/^(?:#~ )?msgstr\[(\d+)\]\s+(.*)/)) {
      lastbuffer = 'msgstr_'+match[1];
      buffer[lastbuffer] = parse_po_dequote(match[2]);

    // continued string
    } else if (/^(?:#~ )?"/.test(lines[i])) {
      buffer[lastbuffer] += parse_po_dequote(lines[i]);

    // something strange
    } else {
      errors.push("Strange line ["+i+"] : "+lines[i]);
    }
  }


  // handle the final entry
  if (typeof(buffer['msgid']) != 'undefined') {
    var msg_ctxt_id = (typeof(buffer['msgctxt']) != 'undefined' &&
                      buffer['msgctxt'].length) ?
                        buffer['msgctxt']+context_glue+buffer['msgid'] :
                        buffer['msgid'];
    var msgid_plural = (typeof(buffer['msgid_plural']) != 'undefined' &&
                       buffer['msgid_plural'].length) ?
                         buffer['msgid_plural'] :
                         null;

    // find msgstr_* translations and push them on
    var trans = [];
    for (var str in buffer) {
      var match;
      if (match = str.match(/^msgstr_(\d+)/))
        trans[parseInt(match[1])] = buffer[str];
    }
    trans.unshift(msgid_plural);

    // only add it if we've got a translation
    // NOTE: this doesn't conform to msgfmt specs
    if (trans.length > 1) rv[msg_ctxt_id] = trans;

    buffer = {};
    lastbuffer = "";
  }


  // parse out the header
  if (rv[""] && rv[""][1]) {
    var cur = {};
    var hlines = rv[""][1].split(/\\n/);
    for (var i=0; i<hlines.length; i++) {
      if (! hlines[i].length) continue;

      var pos = hlines[i].indexOf(':', 0);
      if (pos != -1) {
        var key = hlines[i].substring(0, pos);
        var val = hlines[i].substring(pos +1);

        if (cur[key] && cur[key].length) {
          errors.push("SKIPPING DUPLICATE HEADER LINE: "+hlines[i]);
        } else if (/#-#-#-#-#/.test(key)) {
          errors.push("SKIPPING ERROR MARKER IN HEADER: "+hlines[i]);
        } else {
          // remove begining spaces if any (the perl script keeps them)
          //val = val.replace(/^\s+/, '');
          cur[key] = val;
        }

      } else {
        errors.push("PROBLEM LINE IN HEADER: "+hlines[i]);
        cur[hlines[i]] = '';
      }
    }

    // replace header string with assoc array
    rv[""] = cur;
  } else {
    rv[""] = {};
  }

  // TODO: XXX: if there are errors parsing, what do we want to do?
  // GNU Gettext silently ignores errors. So will we.
  // alert( "Errors parsing po file:\n" + errors.join("\n") );
  if (errors.length) console.warn(errors.join("\n"));

  return rv;
};


var parse_po_dequote = function(str) {
  var match;
  if (match = str.match(/^(?:#~ )?"(.*)"/)) {
    str = match[1];
  }
  str = str.replace(/\\"/g, '"');
  return str;
};

if (argv.indexOf('-h') >= 0 || argv.length < 3) {
  console.log(path.basename(argv[1])+" {-p} {file.po} > {outputfile.json}\n    -p  : do pretty-printing of json data\n");
} else {
  parse(argv[argv[2] === '-p' ? 3:2]);
}

This was extremely helpful. Thanks... I forked it and added some code to let you use it in a node runtime environment. It's a bit rough... doesn't use pretty option, but here it is: https://gist.github.com/2846424