Workshop › Chess › Step 10 of 48

A list of moves

What we are doing

pseudoMoves(color) looks at every square, and for each knight of that color tries the 8 jumps. A jump that stays on the board and does not land on its own piece is a move { from: [r, c], to: [tr, tc] }. An enemy piece there is a capture.

```js
// Every move that follows the pieces' patterns, without checking whether it leaves the king in check.
function pseudoMoves(color) {
  const moves = []
  const add = (r, c, tr, tc) => moves.push({ from: [r, c], to: [tr, tc] })
  for (let r = 0; r < 8; r++) {
    for (let c = 0; c < 8; c++) {
      const piece = board[r][c]
      if (piece[0] !== color) continue
      const kind = piece[1]
      if (kind === 'N') {
        for (const [dr, dc] of KNIGHT) {
          const tr = r + dr
          const tc = c + dc
          if (inside(tr, tc) && board[tr][tc][0] !== color) add(r, c, tr, tc)
        }
      }
    }
  }
  return moves
}
```

What it means

moves starts empty; add pushes one move object onto it.
continue skips to the next square when this one is not ours.
for (const [dr, dc] of KNIGHT) takes each jump and unpacks its two numbers.
board[tr][tc][0] !== color: an empty square's [0] is undefined, so empty squares and enemy pieces pass.
return moves hands back the list.

Your turn

Under inside, leave an empty line and write the comment and pseudoMoves.

Skills: Arrays and objects, Loops

← The knight's jumps as data The king steps too →

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