solution to eight queens puzzle

queens.js

function place (placed, unplaced) {
  if (!unplaced.length) return [placed]
  let validPlacements = []
  unplaced.forEach(unplacedRow => {
    if (placed.every((placedRow, i) => {
      const d = placed.length - i
      return placedRow + d !== unplacedRow && placedRow - d !== unplacedRow
    })) {
      let possibleUnplaced = unplaced.filter(row => row !== unplacedRow)
      validPlacements = [...validPlacements, ...place([...placed, unplacedRow], possibleUnplaced)]
    }
  })
  return validPlacements
}

const rows = []
for (let i = 0; i < 8; i++) rows.push(i)
console.log(place([], rows))