game-of-life.js

const DIM = 5;

/**
 *  -1-DIM  -DIM  +1-DIM
 *  -1       i    +1
 *  -1+DIM  +DIM  +1+DIM
 */
const _compute = (m, out) => {
  for (let x = 1; x < DIM; x++) {
    for (let y = 1; y < DIM; y++) {
      const i = x + y * DIM;
      const nbAlive =
        m[i - 1] +
        m[i + 1] +
        m[i + DIM] +
        m[i + DIM - 1] +
        m[i + DIM + 1] +
        m[i - DIM] +
        m[i - DIM - 1] +
        m[i - DIM + 1];
      if (m[i] && (nbAlive === 2 || nbAlive === 3)) out[i] = 1;
      else if (m[i] && nbAlive === 3) out[i] = 1;
      else out[i] = 0;
    }
  }
  return out;
};

const nextGen = () => {
  m1 = _compute(m1, m2);
};

const createMatrix = () => new Uint8Array((DIM + 2) * (DIM + 2)); // paddedd array

// TEST CASES
let m1 = createMatrix();
// fixtures
m1[1 + DIM] = 1;
m1[3 + DIM] = 1;
m1[4 + DIM] = 1;
m1[1 + DIM * 2] = 1;
m1[2 + DIM * 2] = 1;
m1[DIM * DIM] = 1;

let m2 = createMatrix();


const display = () => {
  for (let x = 1; x < DIM; x++) {
    out = "";
    for (let y = 1; y < DIM; y++) {
      out += m1[x + y * DIM];
    }
    console.log(out);
  }
  console.log("");
};
display(m1);
nextGen();
display(m1);
nextGen();
display(m1);
nextGen();
display(m1);