code: static String getArrayElementStringValue(Node n) {
      return (NodeUtil.isNullOrUndefined(n) || n.isEmpty())
          ? "" : getStringValue(n);
    }
docs: When converting arrays to string using Array.prototype.toString or
  Array.prototype.join, the rules for conversion to String are different
  than converting each element individually.  Specifically, "null" and
  "undefined" are converted to an empty string.
  @param n A node that is a member of an Array.
  @return The string representation.