recursiveReducer

recursiveReducer.js

// Part of my Othello code, no idea if this is the _best_ way to solve this,
// but it's part of my solution

// `grid` is in the parent scope how I write/use this function
function findPiecesToChange(acc, x, y, run, rise) {
  const nextX = x + run
  const nextY = y + rise
  const cell = grid[nextY] && grid[nextY][nextX]

  if (!cell) {
    return null
  }

  if (cell === turn) {
    return acc
  }

  return findPiecesToChange(
    [...acc, { x: nextX, y: nextY }],
    nextX,
    nextY,
    run,
    rise
  )
}