How to get a list of indexes within a certain view radius?

Question

JavaScript

There is a player, his index in the array is 35, the view radius is 2 cells

How to get an array of indices in the view radius?
In this case, it should be taken into account that there can be a wall nearby and there cannot be indices behind the wall.

Answer 1

Something like this:

var
  sizex = 10,
  sizey = 10,
  cur_pos = 35,
  dist = 2,
  list = [];

var
  pos_x = (cur_pos - 1) % sizex,
  pos_y = Math.floor((cur_pos - 1)/sizex);

var
  start_x = (pos_x - dist >= 0) ? pos_x - dist : 0,
  start_y = (pos_y - dist >= 0) ? pos_y - dist : 0,
  end_x = (pos_x + dist < sizex) ? pos_x + dist : sizex - 1,
  end_y = (pos_y + dist < sizey) ? pos_y + dist : sizey - 1;

for (var y = start_y; y <= end_y; y++) {
  for (var x = start_x; x <= end_x; x++) {
    list.push(y * sizex + x + 1);
  }
}

console.log(list);

Answer 2

You can try to finish the fill to account for the distance