code: function defaultComparator(key, a, b) {
      if (key(a) < key(b)) return -1;
      if (key(a) > key(b)) return 1;
      return 0;
  }
docs: Default comparison operation.
  
  @param key {Function} function that extracts a key value (number or string) from a stored object
  @param a {Object} First object
  @param b {Object} Second object
  @returns {boolean} -1, 1, 0 depending on whether a < b, b < a, or a == b