index.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 results = [];

  for (let i = 0; i < n; i++) {
    results.push([]);
  }

  let counter = 1;
  let startColumn = 0;
  let endColumn = n - 1;
  let startRow = 0;
  let endRow = n - 1;

  while (startColumn <= endColumn && startRow <= endRow) {
    // Top row
    for (let i = startColumn; i <= endColumn; i++) {
      results[startRow][i] = counter;
      counter++;
    }
    startRow++;

    // Right column
    for (let i = startRow; i <= endRow; i++) {
      results[i][endColumn] = counter;
      counter++;
    }

    endColumn--;

    // Bottom row
    for (let i = endColumn; i >= startColumn; i--) {
      results[endRow][i] = counter;
      counter++;
    }

    endRow--;

    // start column

    for (let i = endRow; i >= startRow; i--) {
      results[i][startColumn] =counter;
      counter++;
    }
    startColumn++;
  }
  return results;
}

module.exports = matrix;