11-the-matrix.js

// --- Directions
// Write a function that accepts an integer N
// and returns a NxN spiral matrix.
// --- Examples
//   matrix(2)
//     [[1, 2],
//     [4, 3]]
//   matrix(3)
//     [[1, 2, 3],
//     [8, 9, 4],
//     [7, 6, 5]]
//  matrix(4)
//     [[1,   2,  3, 4],
//     [12, 13, 14, 5],
//     [11, 16, 15, 6],
//     [10,  9,  8, 7]]

function matrix(n) {
  const result = []
  let counter=1, startRow=0, endRow=n-1, startCol=0, endCol=n-1
  for(let i=0; i<n; i++){
    result.push([])
  }

  while(startRow<=endRow && startCol<=endCol){
    //Top
  for(let i=startCol; i<=endCol; i++){
    result[startRow][i] = counter
    counter++
  }
  startRow++

  //Right
  for(let i=startRow; i<=endRow; i++){
    result[i][endCol] = counter
    counter++
  }
  endCol--

  //Bottom
  for(let i=endCol; i>=startCol; i--){
    result[endRow][i] = counter
    counter++
  }
  endRow--
  //Left
  for(let i=endRow; i>=startRow; i--){
    result[i][startCol] = counter
    counter++
  }
  startCol++
  }

  return result
}

console.log(matrix(6));