lib.utf.js

                break;
                case 8: case 9: case 10: case 11:
                // 1111 10xx 10xx xxxx 10xx xxxx 10xx xxxx 10xx xxxx
i+=4;
                out[j] = '?';
                break;
                case 12: case 13:
                // 1111 110x 10xx xxxx 10xx xxxx 10xx xxxx 10xx xxxx 10xx xxxx
i+=5;
                out[j] = '?';
                break;
            }
        }
        j++;
    }
    return out.join('');
}