gridtravelermemoized.js

const gridTraveler = (m, n, memo = new Map()) => {
  const key = `${m},${n}`;
  if (memo.has(key)) return memo.get(key);
  if (m === 0 || n === 0) return 0;
  if (m === 1 && n === 1) return 1;
  memo.set(key, gridTraveler(m - 1, n, memo) + gridTraveler(m, n - 1, memo));
  return memo.get(key);
};
console.log(gridTraveler(20, 20));