spiralize.js

var spiralize = function(size) {
  let spiral = [];
  for(let i=0;i<size;i++) {
    spiral[i] = Array(size).fill(0);
  }
  let min = 0;
  let max = size;

  while (min < max ) {
   for(let i=min;i<max;i++) {
      spiral[min][i] = 1; //first row
      spiral[i][max-1] = 1; //last col
      if (max - min > 2) spiral[max-1][i] = 1; //last row
      if (i>=min+2) spiral[i][min] = 1; //first col
      if (i===min+2) spiral[i][min+1] = 1; //curl
    }
    min += 2;
    max -= 2;
  }
  return spiral
}