Chess

A fully playable chess game built on Vue DnD Kit v2. Same architecture as Checkers — every cell is an independent droppable zone, all game logic lives in plain TypeScript.

How it works

DnDProvider
  └── 8×8 grid of ChessCell (makeDroppable)
        └── ChessPiece (makeDraggable)  — rendered when a piece occupies the cell

While dragging, useDnDProvider() exposes the dragged piece so ChessGame can pre-compute all valid target squares and highlight them. Squares where the king would be in check after the move are excluded.

Piece movement

Each piece carries its index and the shared pieces array as the drag payload:

<script setup lang="ts">
  import { makeDraggable } from '@vue-dnd-kit/core';

  const { isDragging } = makeDraggable(
    el,
    { data: () => props.piece },
    () => [index.value, props.pieces]
  );
</script>

Move validation

canReach handles the geometry for each piece type. validateMove wraps it with a check-safety simulation:

function canReach(piece, toRow, toCol, board): boolean {
  // can't land on own piece
  const target = pieceAt(toRow, toCol, board);
  if (target?.color === piece.color) return false;

  switch (piece.type) {
    case 'pawn':   /* forward + diagonal capture */
    case 'knight': /* L-shape */
    case 'bishop': /* diagonal + path clear */
    case 'rook':   /* straight + path clear */
    case 'queen':  /* both */
    case 'king':   /* one step any direction */
  }
}

function validateMove(piece, toRow, toCol): boolean {
  if (!canReach(piece, toRow, toCol, pieces.value)) return false;
  if (wouldBeInCheck(piece, toRow, toCol)) return false;
  return true;
}

Check detection

wouldBeInCheck simulates the board after a move and checks if the moving side's king is attacked:

function wouldBeInCheck(piece, toRow, toCol): boolean {
  const simBoard = pieces.value
    .filter((p) => p.id !== piece.id && !(p.row === toRow && p.col === toCol))
    .concat([{ ...piece, row: toRow, col: toCol }]);
  return isInCheck(piece.color, simBoard);
}

function isInCheck(color, board): boolean {
  const king = board.find((p) => p.color === color && p.type === 'king');
  const opponent = color === 'white' ? 'black' : 'white';
  return board.some((p) => p.color === opponent && canReach(p, king.row, king.col, board));
}

Checkmate & stalemate

After every move the opponent's legal moves are counted. If there are none:

if (!hasLegalMoves(opponent)) {
  winner.value = isInCheck(opponent, pieces.value)
    ? currentTurn.value  // checkmate
    : 'draw';            // stalemate
}

Pawn promotion

Pawns reaching the last rank are automatically promoted to a queen:

const promoted =
  piece.type === 'pawn' &&
  ((piece.color === 'white' && toRow === 0) || (piece.color === 'black' && toRow === 7));

// ...map: promoted ? 'queen' : p.type

See also

• Checkers — the same per-cell droppable pattern with simpler rules.
• DragPreview — customizing the floating preview.

Source

• Example.vue
• ChessGame.vue
• ChessCell.vue
• ChessPiece.vue
• types.ts