res.js

/**
 * @param {number[][]} board
 * @return {void} Do not return anything, modify board in-place instead.
 */
var gameOfLife = function(board) {
  const n = board.length;
  const m = board[0].length;
  const flag = board.map(col => col.map(() => 0));
  
  // Flag
  for (let i = 0; i < n; i++) {
    for (let j = 0; j < m; j++) {
      const ele = board[i][j];
      if (ele) {
        for (let tbIndex = Math.max(i-1, 0); tbIndex < Math.min(i+2, n); tbIndex++) {
          for (let lrIndex = Math.max(j-1, 0); lrIndex < Math.min(j+2, m); lrIndex++) {
            if (tbIndex === i && lrIndex === j) continue;
            flag[tbIndex][lrIndex]++;
          }
        }
        // console.log('new flag', flag)
      }
    }
  }

  // console.log(flag);
  for (let i = 0; i < n; i++) {
    for (let j = 0; j < m; j++) {
      if (board[i][j] && (flag[i][j] < 2 || flag[i][j] > 3)) {
        board[i][j] = 0;
      } else if (board[i][j] && flag[i][j] >= 2 && flag[i][j] <= 3 || !board[i][j] && flag[i][j] === 3) {
        board[i][j] = 1;
      }
    }
  }
};