Sum every cell in a seat-map grid

 1function totalSeats(grid) {
 2  let total = 0;
 3  for (let r = 0; r < grid.length; r++) {
 4    for (let c = 0; c < grid[r].length; c++) {
 5      total += grid[r][c];
 6    }
 7  }
 8  return total;
 9}