function nextGeneration(grid) {
  return grid.map((row, rowIndex) => {
    return row.map((cell, colIndex) => {
      // Non circular grid
      if(!rowIndex || !colIndex || rowIndex == grid.length - 1 || colIndex == row.length - 1) {
        return 0;
      }

      const neighbours = grid[rowIndex   ][colIndex -1] +
                         grid[rowIndex   ][colIndex +1] +
                         grid[rowIndex -1][colIndex -1] +
                         grid[rowIndex -1][colIndex   ] +
                         grid[rowIndex -1][colIndex +1] +
                         grid[rowIndex +1][colIndex -1] +
                         grid[rowIndex +1][colIndex   ] +
                         grid[rowIndex +1][colIndex +1];

      if(neighbours == 3) return 1;
      else if(neighbours != 2) return 0;
      return cell;
    });
  });
}

let lastChar = string => string[string.length - 1]

function lastChar(string) {
  return string[string.length - 1];
}