get_neighbors function for Conway's Game of Life

gistfile1.txt

const getNeighbors = (rowNum, colNum, board) => {
  const neighbors = [];
  for (let r of [rowNum - 1, rowNum, rowNum + 1]) {
    if (board[r] === undefined) {
      continue;
    }
    for (let c of [colNum - 1, colNum, colNum + 1]) {
      if (board[r][c] === undefined) {
        continue;
      }
      if (r === rowNum && c === colNum) {
        continue;
      }
      neighbors.push(board[r][c])
    }
  }
  return neighbors;
};