Set-up a game from scratch

A Game object describes the total state of a chess game, i.e. the played moves, the corresponding positions, the metadata associated to the game (players' names, date, etc...), and the annotations associated to the moves (text comments, alternative moves considered by the annotator, NAGs, etc...).

Since a Game object can hold several alternative moves proposed by an annotator, the moves are represented through a tree-like structure (rather than a linear-like structure, as it would be the case if only the moves actually played were considered). There are two secondary objects used to represent this tree structure:

• Node represents one move together with the annotations associated to this move. It gives access to the positions before and after the move is played (see methods positionBefore and position). It also gives access to the following move in the game (see next), and the alternative moves - aka. the variations - if any (see variations).
• Variation represents a sequence of Node objects, aka a sequence of moves. A Game object holds a so-called "main variation" (see mainVariation) that is the root of the tree structure.

You can create a Game object from scratch as follows:

const { Game, pgnWrite } = require('kokopu');

const game = new Game();

// Set the player's names and event
game.playerName('w', 'Alice');
game.playerName('b', 'Bob');
game.event('1st International Open of Whatever');

// Start the main variation
let current = game.mainVariation(); // `current` points at a `Variation` object here
current = current.play('e4'); // `current` points at a `Node` object from now on
current = current.play('e5');

// Let's introduce an alternative to move 1...e5
let alternative1 = current.addVariation(); // `alternative1` points at a `Variation` object here
alternative1 = alternative1.play('c5'); // `alternative1` points at a `Node` object from now on
alternative1 = alternative1.play('Nf3');

// Let's introduce another alternative to move 1...e5
let alternative2 = current.addVariation(); // `alternative2` points at a `Variation` object here
alternative2 = alternative2.play('e6'); // `alternative2` points at a `Node` object from now on
alternative2 = alternative2.play('d4');

// Back to the main variation
current = current.play('Bc4');
current = current.play('Nc6');
current = current.play('Qh5');
current = current.play('Nf6');
current = current.play('Qxf7#');
current.comment('That is the Scholar\'s Mate');
game.result('1-0');

// Display an ASCII-art representation of the game.
console.log(game.ascii());

// Event: 1st International Open of Whatever
// White: Alice
// Black: Bob
// 1.e4
// 1...e5
//  |
//  +- 1...c5
//  |  2.Nf3
//  |
//  +- 1...e6
//  |  2.d4
//  |
// 2.Bc4
// 2...Nc6
// 3.Qh5
// 3...Nf6
// 4.Qxf7# That is the Scholar's Mate
// 1-0

// Generate the PGN-representation of the game.
console.log(pgnWrite(game));

// [Event "1st International Open of Whatever"]
// [Site "?"]
// [Date "????.??.??"]
// [Round "?"]
// [White "Alice"]
// [Black "Bob"]
// [Result "1-0"]
//
// 1. e4 e5 (1... c5 2. Nf3) (1... e6 2. d4) 2. Bc4 Nc6 3. Qh5 Nf6 4. Qxf7# {That
// is the Scholar's Mate} 1-0