Power set generator.

power_set_generator.js

var power_set_generator = function(set) {
  var _index=0, _set=set, _max_size= 1<<set.length;
  return Object.create(Object.prototype, {
    next : { value : function() {
      var result = [], n=_index,i=0;
      if (_index >= _max_size) return;
      for (; n; n>>=1, i+=1) if (n & 1) result.push(_set[i]);
      _index+=1;
      return result;
    }}
  });
};

// var generator = power_set_generator(["a","b","c"]);

/*
while (val = generator.next()) {
  console.log(val);
}
*/