For funsies

game-of-life.js

const grid = buildGrid(20, 50, [
  (10 * 50) + 20,
  (10 * 50) + 21,
  (10 * 50) + 22,
  (10 * 50) + 23,
  (10 * 50) + 24,
  (10 * 50) + 25,
  (10 * 50) + 26,
  (10 * 50) + 27,
  (10 * 50) + 28,
]);

function buildGrid(rows, columns, active = []) {
  const cells = [];
  const totalCells = rows * columns;
  const grid = { rows, columns, cells };
  
  for (let i = 0; i < totalCells; i++) {
    cells.push(active.includes(i));
  }
  
  return grid;
}

function drawGrid(grid) {
  const line = [];
  
  grid.cells.forEach((cell, i, { length }) => {
    if (i % grid.columns === 0 || i === length) {
      if (line.length) console.log(line.join(''));
      line.length = 0;
    }
    
    if (cell) line.push('🦊')
    else line.push(' ');
  });
  
  if (line.length) console.log(line.join(''));
}

function updateGrid(grid) {
  grid.cells = grid.cells.map((cell, i) => isAlive(cell, i, grid));
}

function isAlive(cell, i, grid) {
  const top = grid.cells[i - grid.columns];
  const topLeft = grid.cells[i - grid.columns - 1];
  const topRight = grid.cells[i - grid.columns + 1];
  const bottom = grid.cells[i + grid.columns];
  const bottomLeft = grid.cells[i + grid.columns - 1];
  const bottomRight = grid.cells[i + grid.columns + 1];
  const left = grid.cells[i - 1];
  const right = grid.cells[i + 1];
  const count = top + bottom + left + right + topLeft + topRight + bottomLeft + bottomRight;
  
  return cell ? count > 1 && count < 4 : count === 3;
}

function tick() {
  console.clear();
  updateGrid(grid);
  drawGrid(grid);
}

function start() {
  setInterval(tick, 1000);
}

drawGrid(grid);
start();