kokopu/doc_src/migration/migrate_to_4.md

A JavaScript/TypeScript library implementing the chess game rules and providing tools to read/write the standard chess file formats.

---
title: Migrate to 4.x
---


Migrate to 4.x
==============

Kokopu version 4.0.0 introduces some breaking changes with regard to the previous versions.
Those changes may require some fixes or adjustments in your codebase when upgrading Kokopu
from 3.x to 4.0.0 (or any subsequent version).

To upgrade from an older version (1.x or 2.x), follow the [migration guide to 3.x](migrate_to_3.md) beforehand.



Game.round() (getter and setter)
--------------------------------

As of 4.0.0, the getter {@link Game.round | Game.round()} returns a positive integer instead of a string,
and similarly the corresponding setter expects a positive integer (or any string that can be converted to a positive integer).

To support multipart rounds, Kokopu 4.0.0 introduces {@link Game.subRound | Game.subRound()} and {@link Game.subSubRound | Game.subSubRound()}.
Hence, when for instance a PGN file contains a `Round` header such as `[Round "4.1.2"]`, the header is parsed such that
{@link Game.round | Game.round()} returns `4`, {@link Game.subRound | Game.subRound()} returns `1`, and
{@link Game.subSubRound | Game.subSubRound()} returns `2`.

Method {@link Game.fullRound | Game.fullRound()} can be considered as a replacement of the former {@link Game.round | Game.round()} getter:
this method concatenates the round, sub-round and sub-sub-round in a single string using dot characters as separators,
i.e. returns string similar to the value of the underlying `Round` header if the {@link Game} is loaded from a PGN file.