Possible error in the code expression of vector clocks (chapter3)

[Freeman97]

Sorry for my bad English. I think there is something wrong with the code of merging two vector clocks:

VectorClock.prototype.merge = function(other) {
  var result = {}, last,
      a = this.value,
      b = other.value;
  // This filters out duplicate keys in the hash
  // But why join b and the key of a?
  (Object.keys(a)
    .concat(b))
    .sort()
    .filter(function(key) {
      var isDuplicate = (key == last);
      last = key;
      return !isDuplicate;
    }).forEach(function(key) {
      result[key] = Math.max(a[key] || 0, b[key] || 0);
    });
  this.value = result;
};

The code join the key of a and b, but not the key of b.

[Freeman97]

Sorry for not reading the pull request : (