Arrange numbers 1 to N^2 in a Zig-Zag Matrix in ascending order

<script>

// Javascript program for
// the above approach

// Function to print the pattern
function printPattern(n)
{

  // N * N matrix to store the
  // values
  let arr = new Array(n);
  
  // Loop to create 2D array using 1D array
    for (let i = 0; i < arr.length; i++) {
        arr[i] = new Array(2);
    }
 
  arr[0][0] = 1;
 
  // Fill the values of
  // upper triangle
  for (let i = 0; i < n; i++)
  {
    if (i > 0)
    {
      arr[i][0] = arr[i - 1][0] +
                      i + 1;
    }
    for (let j = 1; j < n - i; j++)
    {
      arr[i][j] = arr[i][j - 1] +
                      i + j;
    }
  }
 
  // Fill the values of
  // lower triangle
  arr[1][n - 1] = arr[n - 1][0] + 1;
  let div = 0;
 
  for (let i = 2; i < n; i++)
  {
    div = n - 2;
    for (let j = n - i; j < n; j++)
    {
      if (j == n - i)
      {
        arr[i][j] = arr[i - 1][j + 1] + 1;
      }
      else
      {
        arr[i][j] = arr[i][j - 1] + div;
        div--;
      }
    }
  }
 
  // Print the array
  for (let i = 0; i < n; i++)
  {
    for (let j = 0; j < n; j++)
    {
      document.write(arr[i][j] + " ");
    }
    document.write("<br/>");
  }
}

// Driver code

    // Given size of matrix
  let N = 4;
 
  // Function Call
  printPattern(N);
    
    // This code is contributed by susmitakundugoaldanga.
</script>