Porting invRegex.py to Javascript (Node.js)

Question

I have been trying to port invRegex.py to a node.js implementation for a while, but I\'m still struggling with it. I already have the regular expression parse tree thanks to

Answer 1

How about this:

var tokens = [
    ['0', '00', '01', '1', '10', '11'],
    ['@'],
    ['a', 'b', 'c', 'd', 'e', 'f'],
];

function cartesianProductOf(arr, callback) {
  var cur = [];
  var f = function(i) {
    if (i >= arr.length) {
      callback(cur.join(''));
      return
    }
    for (var j=0; j